Tuesday, in Munich.
1310.6402
Interpreting the ionization sequence in AGN emission-line spectra
Richardson et al
Investigate the physical cause of the great range n the ionization level seen in the spectra of narrow lined ACN. Mean field independent component analysis: identifies examples of SDSS galaxies whose spectra are not dominated by emission due to SF, designate those as AGN. Assemble high S/N ratio composite spectra of a sequence of these AGN defined by the ionization level of their narrow-line region (NLR), extending down to very low-ionization cases. Used a local optimally emitting cloud (LOC) model to fit emission-line ratios in this AGN sequence. These included the weak lines that can be measured only in the co-added spectra, providing consistency checks on strong line diagnostics. After integrating over a wide range of radii and densities, models indicate that the radial extent of the NLR is the major parameter in determining the position of high to moderate ionization AGN along the sequence, providing a physical interpretation for their systematic variation. Higher ionization AGN contain optimally emitting clouds that are more concentrated towards the central continuum source than in lower ionization AGN. LOC models indicate that for the objects that lie on the AGN sequence, the ionizing luminosity is anti correlated with the NLR ionization level, and hence anti correlated with the radial concentration and physical extend of the NLR. A possible interpretation that deserves further exploration is that the ionization sequence might be an age sequence where low ionization objects are older and have systematically cleared out their central regions by radiation pressure. Consider that the AGN sequence instead represent a mixing curve of SF and AGN spectra, but argue that whie many galaxies do have this type of composite spectra, this AGN sequence appears to be a special set of objects with negligible SF excitation.
1310.6459
Neutrino clustering around spherical dark matter halos
LoVerde, Zaldarriaga
CDM haloes from within a smoothly distributed BG of relic neutrinos -- at least some of which are massive and non-relativistic at late times. Calculate the accumulation of massive neutrinos around spherically collapsing CDM haloes in a cosmological background. Identify the physical extent of the "neutrino halo" in the spherical collapse model, which is large in comparison with the virial radius of the DM, and conditions under which neutrinos reaching the CDM halo will remain bound to the halo at late times. Calculate the total neutrino mass and bound neutrino mass associated with isolated spherical haloes for several neutrino mass hierarchies and provide fitting formulae for these quantities in terms of the CDM halo mass and the masses of the individual neutrino species.
1310.6495
Giant low surface brightness galaxies : evolution in isolation
Das
GLSB galaxies are amongst the most massive spiral galaxies known in the Universe. Although they fall in the class of late type spiral galaxies, their properties are far more extreme. They have very faint stellar disks that are extremely rich in neutral hydrogen gas but low in SF and hence low in surface brightness. They often have bright bulges that are similar to those found in early type galaxies. The bulges can host low luminosity AGN that have relatively low mass BHs. GLSB galaxies are usually isolated systems and are rarely found to be interacting with other galaxies. In fact many GLSB galaxies are found under dense regions close to the edges of voids. These galaxies have very massive DM halos that also contribute to their stability and lack of evolution. In this paper, briefly review the properties of this unique class of galaxies and conclude that both their isolation and their massive DM haloes have led to the low SFRs and the slower rate of evolution in these galaxies.
1310.6507
A Bcool spectropolarimetric survey of over 150 solar-type stars
Marsden, et al
Over 150 solar-type stars chosen mainly from planet search databases have been observed with spectropolarimeters at Bernard Lyot and at CFHT. These single 'snapshot' observations have been used to detect the presence of B-fields on 40% of the sample, with the highest detection rates occurring for the youngest stars. From the observations, determine the mean surface longitudinal field (or an upper limit for stars without detections) and the chromospheric surface fluxes, and find that the upper envelope of the absolute value of the mean surface longitudinal field is directly correlated to the chromospheric emission from the star and increases with rotation rate and decreases with age.
1310.6557
The occultation of Arcturus in the Vatican
Sigismondi
Dome of Saint Peter's Basilica occults Arcturus. Youtube video available.
1310.6653
TADPOL: a 1.3 mm survey of dust polarization in star-forming cores and regions
Hull, … Bower, … et al
Present results of 1.3 mm dust polarization observations towards 29 SF cores and 8 hig-mass SF regions, mapped with 2.5" resolution at CARMA. Find: (1) a subset of the sources have consistent B-field orientations between the large scales measured by single-dish sub millimeter telescopes (with ~20" resolution) and the small scales measured by CARMA. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields, possibly because there is less twisting of the B-fields to reduce the polarization fraction. This suggests that in at least some sources, the B-fields play a role in regulating the infall of material over many orders of magnitude, all the way down to ~1000 AU protostellar envelope scales. (2) Even in the sources with consistent large-to-small-scale field orientations, the magnetic fields in the cores are misaligned with outflows from the central protostars. Furthermore, the sources with lower polarization fractions tend to have B-fields that are preferentially perpendicular to outflows, which suggests that in these sources the B-fields have been wrapped up by envelope rotation. (3) Finally, find that all sources exhibit the so-called "polarization hole" effect, where the fractional polarization drops significantly near the total intensity peak.
1310.6688
DAMIC: a novel dark matter experiment
The DAMIC collaboration
DAMIC (Dark Matter in CCDs) is a DM experiment that has sensitivity to DM particles with m<10 GeV. Due to low readout noise (rms ~3 e-), this instrument is able to reach a detection threshold below 0.5 keV nuclear recoil energy, making the search for DM particles with low mass possible. Report on early results and experience gained from a detector that has been running at SNOLAB since Dec 2012. Also discuss the measured and expected BGs and present the plan for future detectors to be installed in 2014.
1310.6716
Search for primordial non-Gaussianity in the quasars of SDSS-III BOSS DR9
Karagiannis, Shanks, Ross
Analyze 22k quasars of 2.2<z<2.9 on BOSS. Fit the clustering results with a LCDM model to calculate the linear bias of the quasar sample, b=3.74pm0.12. The measured value of bias is consistent with the findings of White+ (2012), where they analyze almost the same quasar sample, although only in the range s<40 Mpc/h. Fitting the standard cosmological model at small and intermediate scales (3-120 Mpc/h) of the quasar clustering produces a rejection at the 2.2 sigma significance level. At larger scales, observe and excess or plateau in the clustering correlation function. Including this large-scale feature in the fit produces a rejection of LCDM at the 2.7 sigma level. By fitting a model that incorporates a scale dependent additional term in the bias introduced by primordial non-Gaussianity of the local type, calculate the amplitude of the deviation from the Gaussian ICs at 70<f_NL<190 at the 95% CL. Apply stricter cuts on Galactic extinction, where after keeping regions with A_r<0.14 mag, measure 81<f_NL<170 at 95% CL. In this case the goodness-of-fit of LCDM shows a rejection of the model at a significance level of 1.7 sigma. Investigating systematics further, make corrections according to the methods of Ross+2011, Ho+2012 and Ross+2011, 2012b, with the f_NL measurements after the application of the two methods being consistent with each other. Consider as the final results on non-Gaussianity those originating after the correction of the sample with the weights methods of Ross+2011, 2012b, giving 46<f_NL<158 at 95% CL. The rejection value of LCDM in this case is at the 2.3 sigma level.
Wednesday, October 30, 2013
Monday, October 28, 2013
Day 538
Monday.
1310.6362
An ALMA survey of submillimetre galaxies in the extended Chandra deep field south: the far-infrared properties of SMGs
Swinbank, et al
In ECDFS, 99 SMGs in 870um (ALMA), with 24um and radio imaging of this field; deb lend Herschel/SPIRE imaging of this region to extract their FIR fluxes and colors. The median photometric redshifts for ALMA LESS SMGs (detected in at least 2 SPIRE bands) increases with wavelength of the peak in their SEDs, with z=2.3, 2.5, 3.5 for the 250, 350 and 500um peakers respectively. Find that 34 ALESS SMGs do not have a >3-sigma counterpart at 250, 350, or 500 um. These galaxies have a median photometric redshift of z=3.3pm0.5, which is higher than the full ALESS SMG sample; z=2.5pm0.2. Using the photo-z together with the 250-870um photometry, estimate the FIR luminosities and characteristic dust temperature of each SMG. The median IR luminosity of the S_870um>2mJy SMGs is L_IR=3.0e12 Lsun (SFR=300pm30 Msun/yr). At a fixed luminosity, the characteristic dust temperature of these high-z SMGs is 2-3K lower than comparably luminous galaxies at z=0, reflecting the more extended SF occurring in these systems. By extrapolating the 870 um number counts to S_870um=1mJy, show that the contribution of S_870um>1mJy SMGs to the cosmic SF budget is 20% of the total over 1<z<4. Derive a median dust mass for these SMGs of M_d=3.6e8 Msun and by adopting an appropriate gas-to-dust ratio, estimate an average molecular mass of M_H2=4.2e10 Msun. Finally, use estimate of the H2 masses to show that SMGs with S_870um>1mJy contain ~10% of the z~2 volume-averaged H2 mass density at this epoch.
1310.6363
An ALMA survey of sub millimeter galaxies in the Extended Chandra Deep Field South: The redshift distribution and evolution of sub millimeter galaxies
Simpson, et al
Present the photo-z distribution of SMGs (unbiased sample of 870um selected objects) of 96 SMG, 77 of which have 4-19 band, optical-NIR photometry. Model SEDs for these 77 SMGs, deriving a median photo-z of 2.3pm0.1. The remaining 19 were stacked to confirm they are not spurious detections. Assuming these sources have an absolute H-band magnitude distribution comparable to that of a complete sample of z~1-2 SMGs, demonstrate that the undetected SMGs lie at higher z, raising the median redshift for SMGs to z=2.5pm0.2. Show that the proportion of galaxies undergoing and SMG phase at z>3 is 35pm5% of the total population. Derive a median stellar mass for SMGs of M*=8e10 Msun, but caution that there are significant systematic uncertainties in M* estimates; up to x5 for individual sources. Assuming the SF activity in SMGs has a timescale of ~100 Myr, show that their descendants at z~0 would have a space density and M_H distribution which are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local elliptical broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.
1310.6364
An ALMA survey of sub millimeter galaxies in the Extended Chandra Deep Filed South: The AGN fraction and X-ray properties of sub millimeter galaxies
Wang et al
The large gas and dust reservoirs of SMGs could potentially provide ample fuel to trigger an AGN, but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available sub millimeter surveys. Set improved constraints on the AGN fraction and X-ray properties of the SMGs with ALMA and Chandra observations in the ECDFS. This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submm-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA ECDFS sub millimeter survey (ALESS). Found 10 X-ray sources associated with SMGs (median z=2.3), of which where identified as AGNs from cross-checking. The other 2 X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their SF activity. 6 of the 8 SMG-AGNs are moderately/highly absorbed, with N_H>1e23 cm^-2. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of 17+16-6% for AGNs with rest-frame 0.5-8 keV absorption-corrected luminosity >7.8e42 erg/s; provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and found 4 potential SMG-AGNs in the stacking sample.
1310.6365
Dwarfs walking in a row. The filamentary nature of the NGC3109 association
Bellazzini et al
Reconsider the association, whose members are: NGC3109, Antila, Sextans A and Sextans B. Find that the original members of the association, together with the recently discovered and adjacent dirt Leo P, form a very tight and elongated configuration in space. All these galaxies lie within ~100 kpc of a line that is ~1070 kpc long, from one extreme (NGC3109) to the other (Leo P), and they show a gradient in the Local Group standard of rest velocity with a total amplitude of 43 kpm/s Mpc and a rms scatter of just 16.8 km/s. It is shown that the reported configuration is exceptional given the known dwarf galaxies in the Local Group and its surroundings. Conclude that (a) Leo P is likely an additional member of the NGC 3109 association, and (b) the association is highly order in space and velocity, and it is very elongated, suggesting that it has been originated by a tidal interaction or it was accreted as a filamentary sub-structure.
1310.6366
Pan-STARRS1: galaxy clustering in the small area survey 2
Farrow, Cole, Metcalfe, … Kaiser, et al
PS1 is currently obtaining imaging in 5 bands (grizy) for 3pi stradian survey, one of the largest optical surveys ever conducted. The finished survey will have spatially varying depth, due to the survey strategy. This paper presents a method to correct galaxy number counts and galaxy clustering for this potential systematic based on a simplified signal to noise measurement. A star and galaxy separation method calibrated using realistic synthetic images is also presented, along with an approach to mask bright stars. By using techniques on a ~69 sq. deg. region of science verification data this paper shows PS1 measurements of the 2pt angular correlation function as a function of apparent magnitude agree with measurements from deeper, smaller surveys. Clustering measurements appear reliable down to a magnitude limit of fps<22.5. Additionally, stellar contamination and false detection issues are discussed and quantified. This work is the second of two papers which pave the way for the exploitation of the full 2pi survey for studies of LSS.
1310.6367
NGC1277: a massive compact relic galaxy in the nearby Universe
Trujillo et al
As early as 10 Gyr ago [redshift?], galaxies with more than 1e11 Msun in [stellar mass] already existed. While most of these massive galaxies must have subsequently transformed through on-going SF and mergers with other galaxies, a small fraction (<0.1%) may have survived untouched till today. Searches for such relic galaxies, useful windows to explore the early Universe, have been inconclusive to date: galaxies with masses and sizes like those observed at high z (M*>1e11 Msun; Re<1.5 kpc) have been found in the local Universe, but their stars are far too young for the galaxy to be a relic. This paper explores the first case of a nearby galaxy, NGC1277 (in the Perseus cluster at a distance of 73 Mpc [distance from cluster center? or from us?]), which fulfills all the criteria to be considered a relic galaxy. Using deep optical spectroscopy, derive the SFH along the structure of the galaxy: the stellar populations are uniformly old (>10 Gyr) with no evidence for more recent SF episodes. The metallicity of their stars is super-solar ([Fe/H]=0.20pm0.04) and alpha enriched ([alpha/Fe]=0.4 pm 0.1). This suggests a very short formation time scale for the bulk of stars of this galaxy. This object also rotates very fast (Vrot~300 km/s) and has a large velocity dispersion (sigma>300 km/s). NGC1277 will allow future explorations in full detail of properties such as the structure, internal dynamics, metallicity, dust content and IMF at around 10-12 Gyr back in time when the first massive galaxies were built.
1310.6368
The Pan-STARRS1 small area survey 2
Metcalfe et al
PS1 is acquiring multi-epoch imaging in 5 bands (grizy) over the entire sky north of declination -30 deg (the 3pi survey). In July 2011 a test area of ~70 sq deg. was observed to the expected final depth of the main survey. In this, the first of a series of papers targeting the galaxy count and clustering properties of the combined multi-epoch test area data, present a detailed investigation into the depth of the survey and the reliability of the PS1 analysis software. Show that the PS1 reduction software can recover the properties of fake sources, and show good agreement between the magnitudes measured by PS1 and those from SDSS. Also examine the number of false detections apparent in the PS1 data. Comparisons show that the test are survey is somewhat deeper than the SDSS in all bands, and in particular, the z band approaches the depth of the stacked stripe82 data.
1310.6362
An ALMA survey of submillimetre galaxies in the extended Chandra deep field south: the far-infrared properties of SMGs
Swinbank, et al
In ECDFS, 99 SMGs in 870um (ALMA), with 24um and radio imaging of this field; deb lend Herschel/SPIRE imaging of this region to extract their FIR fluxes and colors. The median photometric redshifts for ALMA LESS SMGs (detected in at least 2 SPIRE bands) increases with wavelength of the peak in their SEDs, with z=2.3, 2.5, 3.5 for the 250, 350 and 500um peakers respectively. Find that 34 ALESS SMGs do not have a >3-sigma counterpart at 250, 350, or 500 um. These galaxies have a median photometric redshift of z=3.3pm0.5, which is higher than the full ALESS SMG sample; z=2.5pm0.2. Using the photo-z together with the 250-870um photometry, estimate the FIR luminosities and characteristic dust temperature of each SMG. The median IR luminosity of the S_870um>2mJy SMGs is L_IR=3.0e12 Lsun (SFR=300pm30 Msun/yr). At a fixed luminosity, the characteristic dust temperature of these high-z SMGs is 2-3K lower than comparably luminous galaxies at z=0, reflecting the more extended SF occurring in these systems. By extrapolating the 870 um number counts to S_870um=1mJy, show that the contribution of S_870um>1mJy SMGs to the cosmic SF budget is 20% of the total over 1<z<4. Derive a median dust mass for these SMGs of M_d=3.6e8 Msun and by adopting an appropriate gas-to-dust ratio, estimate an average molecular mass of M_H2=4.2e10 Msun. Finally, use estimate of the H2 masses to show that SMGs with S_870um>1mJy contain ~10% of the z~2 volume-averaged H2 mass density at this epoch.
1310.6363
An ALMA survey of sub millimeter galaxies in the Extended Chandra Deep Field South: The redshift distribution and evolution of sub millimeter galaxies
Simpson, et al
Present the photo-z distribution of SMGs (unbiased sample of 870um selected objects) of 96 SMG, 77 of which have 4-19 band, optical-NIR photometry. Model SEDs for these 77 SMGs, deriving a median photo-z of 2.3pm0.1. The remaining 19 were stacked to confirm they are not spurious detections. Assuming these sources have an absolute H-band magnitude distribution comparable to that of a complete sample of z~1-2 SMGs, demonstrate that the undetected SMGs lie at higher z, raising the median redshift for SMGs to z=2.5pm0.2. Show that the proportion of galaxies undergoing and SMG phase at z>3 is 35pm5% of the total population. Derive a median stellar mass for SMGs of M*=8e10 Msun, but caution that there are significant systematic uncertainties in M* estimates; up to x5 for individual sources. Assuming the SF activity in SMGs has a timescale of ~100 Myr, show that their descendants at z~0 would have a space density and M_H distribution which are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local elliptical broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.
1310.6364
An ALMA survey of sub millimeter galaxies in the Extended Chandra Deep Filed South: The AGN fraction and X-ray properties of sub millimeter galaxies
Wang et al
The large gas and dust reservoirs of SMGs could potentially provide ample fuel to trigger an AGN, but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available sub millimeter surveys. Set improved constraints on the AGN fraction and X-ray properties of the SMGs with ALMA and Chandra observations in the ECDFS. This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submm-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA ECDFS sub millimeter survey (ALESS). Found 10 X-ray sources associated with SMGs (median z=2.3), of which where identified as AGNs from cross-checking. The other 2 X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their SF activity. 6 of the 8 SMG-AGNs are moderately/highly absorbed, with N_H>1e23 cm^-2. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of 17+16-6% for AGNs with rest-frame 0.5-8 keV absorption-corrected luminosity >7.8e42 erg/s; provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and found 4 potential SMG-AGNs in the stacking sample.
1310.6365
Dwarfs walking in a row. The filamentary nature of the NGC3109 association
Bellazzini et al
Reconsider the association, whose members are: NGC3109, Antila, Sextans A and Sextans B. Find that the original members of the association, together with the recently discovered and adjacent dirt Leo P, form a very tight and elongated configuration in space. All these galaxies lie within ~100 kpc of a line that is ~1070 kpc long, from one extreme (NGC3109) to the other (Leo P), and they show a gradient in the Local Group standard of rest velocity with a total amplitude of 43 kpm/s Mpc and a rms scatter of just 16.8 km/s. It is shown that the reported configuration is exceptional given the known dwarf galaxies in the Local Group and its surroundings. Conclude that (a) Leo P is likely an additional member of the NGC 3109 association, and (b) the association is highly order in space and velocity, and it is very elongated, suggesting that it has been originated by a tidal interaction or it was accreted as a filamentary sub-structure.
1310.6366
Pan-STARRS1: galaxy clustering in the small area survey 2
Farrow, Cole, Metcalfe, … Kaiser, et al
PS1 is currently obtaining imaging in 5 bands (grizy) for 3pi stradian survey, one of the largest optical surveys ever conducted. The finished survey will have spatially varying depth, due to the survey strategy. This paper presents a method to correct galaxy number counts and galaxy clustering for this potential systematic based on a simplified signal to noise measurement. A star and galaxy separation method calibrated using realistic synthetic images is also presented, along with an approach to mask bright stars. By using techniques on a ~69 sq. deg. region of science verification data this paper shows PS1 measurements of the 2pt angular correlation function as a function of apparent magnitude agree with measurements from deeper, smaller surveys. Clustering measurements appear reliable down to a magnitude limit of fps<22.5. Additionally, stellar contamination and false detection issues are discussed and quantified. This work is the second of two papers which pave the way for the exploitation of the full 2pi survey for studies of LSS.
1310.6367
NGC1277: a massive compact relic galaxy in the nearby Universe
Trujillo et al
As early as 10 Gyr ago [redshift?], galaxies with more than 1e11 Msun in [stellar mass] already existed. While most of these massive galaxies must have subsequently transformed through on-going SF and mergers with other galaxies, a small fraction (<0.1%) may have survived untouched till today. Searches for such relic galaxies, useful windows to explore the early Universe, have been inconclusive to date: galaxies with masses and sizes like those observed at high z (M*>1e11 Msun; Re<1.5 kpc) have been found in the local Universe, but their stars are far too young for the galaxy to be a relic. This paper explores the first case of a nearby galaxy, NGC1277 (in the Perseus cluster at a distance of 73 Mpc [distance from cluster center? or from us?]), which fulfills all the criteria to be considered a relic galaxy. Using deep optical spectroscopy, derive the SFH along the structure of the galaxy: the stellar populations are uniformly old (>10 Gyr) with no evidence for more recent SF episodes. The metallicity of their stars is super-solar ([Fe/H]=0.20pm0.04) and alpha enriched ([alpha/Fe]=0.4 pm 0.1). This suggests a very short formation time scale for the bulk of stars of this galaxy. This object also rotates very fast (Vrot~300 km/s) and has a large velocity dispersion (sigma>300 km/s). NGC1277 will allow future explorations in full detail of properties such as the structure, internal dynamics, metallicity, dust content and IMF at around 10-12 Gyr back in time when the first massive galaxies were built.
1310.6368
The Pan-STARRS1 small area survey 2
Metcalfe et al
PS1 is acquiring multi-epoch imaging in 5 bands (grizy) over the entire sky north of declination -30 deg (the 3pi survey). In July 2011 a test area of ~70 sq deg. was observed to the expected final depth of the main survey. In this, the first of a series of papers targeting the galaxy count and clustering properties of the combined multi-epoch test area data, present a detailed investigation into the depth of the survey and the reliability of the PS1 analysis software. Show that the PS1 reduction software can recover the properties of fake sources, and show good agreement between the magnitudes measured by PS1 and those from SDSS. Also examine the number of false detections apparent in the PS1 data. Comparisons show that the test are survey is somewhat deeper than the SDSS in all bands, and in particular, the z band approaches the depth of the stacked stripe82 data.
Sunday, October 27, 2013
Day 537
Sunday.
1310.6351
Embedded lensing time delays, the Fermat potential, and the integrated Sachs-Wolfe effect
Chen, Kantowski, Dai
* "The lens equation, which relates the placement and distortion of the images to the real source position in the thin-lens scenario, is obtained by extremizing the time of arrival among all the null paths from the source to the observer (Fermat's principle)" (From the abstract of Frittelli, Kling, Newman 2002)
Derive the Ferman potential for a spherically symmetric lens embedded in an FLRW cosmology and use it to investigate the late-time ISW. Present a simple analytical expression for the temperature fluctuation in the CMB across such a lens as a derivative of the lens' Fermat potential. This formalism is applicable to both linear and NL density evolution scenarios, to arbitrarily large density contrasts, and to all open and closed BG cosmologies. Apply this formalism to interpret the observed ISW effects extracted through stacking large numbers of cosmic voids and clusters. For structures co-expanding with the BG cosmology, i.e., for time-independent density contrasts, find that the gravitational lensing time delay alone can produce fluctuations in the CMB temperature of the order of recent observations by Planck.
1310.6358
Confirmation of small dynamical and stellar masses for extreme emission line galaxies at z~2
Maseda, et al
Spectroscopic observations from LBT and VLT reveal kinematically narrow lines (~50 km/s) for a sample of 14 Extreme Emission Line Galaxies (EELGs) at 1.4<z<2.3. These measurements imply that the total dynamical masses of these systems are low (<3e9 Msun). Their large [O III] 5007 EWs (500-1100 A) and faint blue continuum emission imply young ages of 10-100 Myr and stellar masses of 1e8-9 Msun, confirming the presence of a violent SB. The dynamical masses represent the first such determinations for low-mass galaxies at z>1. The stellar mass formed in this vigorous SB phase represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggest that SN-driven winds must be of critical importance in the subsequent evolution of these systems.
1310.6351
Embedded lensing time delays, the Fermat potential, and the integrated Sachs-Wolfe effect
Chen, Kantowski, Dai
* "The lens equation, which relates the placement and distortion of the images to the real source position in the thin-lens scenario, is obtained by extremizing the time of arrival among all the null paths from the source to the observer (Fermat's principle)" (From the abstract of Frittelli, Kling, Newman 2002)
Derive the Ferman potential for a spherically symmetric lens embedded in an FLRW cosmology and use it to investigate the late-time ISW. Present a simple analytical expression for the temperature fluctuation in the CMB across such a lens as a derivative of the lens' Fermat potential. This formalism is applicable to both linear and NL density evolution scenarios, to arbitrarily large density contrasts, and to all open and closed BG cosmologies. Apply this formalism to interpret the observed ISW effects extracted through stacking large numbers of cosmic voids and clusters. For structures co-expanding with the BG cosmology, i.e., for time-independent density contrasts, find that the gravitational lensing time delay alone can produce fluctuations in the CMB temperature of the order of recent observations by Planck.
1310.6358
Confirmation of small dynamical and stellar masses for extreme emission line galaxies at z~2
Maseda, et al
Spectroscopic observations from LBT and VLT reveal kinematically narrow lines (~50 km/s) for a sample of 14 Extreme Emission Line Galaxies (EELGs) at 1.4<z<2.3. These measurements imply that the total dynamical masses of these systems are low (<3e9 Msun). Their large [O III] 5007 EWs (500-1100 A) and faint blue continuum emission imply young ages of 10-100 Myr and stellar masses of 1e8-9 Msun, confirming the presence of a violent SB. The dynamical masses represent the first such determinations for low-mass galaxies at z>1. The stellar mass formed in this vigorous SB phase represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggest that SN-driven winds must be of critical importance in the subsequent evolution of these systems.
Day 536
Friday. Saturday.
1310.6209
Toward a hybrid dynamo model for the Milky Way
Gressel, Elstner, Ziegler
MW's B-field is now modeled with an unprecedented level of detail and complexity, based on the rapidly increasing all-sky data of Faraday rotation measures and polarized synchrotron radiation. Complement this heuristic approach with a physically motivated, quantitative Galactic dynamo model: a model that allows for the evolution of the system as a whole, instead of just solving the induction equation for a fixed static disc. Building on the framework of mean-field magnetohydrodynamics and extending it to the realm of hybrid evolution, perform three-dimensional global simulations of the Galactic disc. Closure coefficients embodying the mean-field dynamo are calibrated against resolved box simulations of SN-driven interstellar turbulence. The emerging dynamo solutions comprise a mixture of dominant axisymmetric S0 mode, with even parity and a subdominant A0 mode, with odd parity. Notably, such a superposition of modes creates a strong localized vertical field on one side of the Galactic disc. Moreover, find significant radial pitch angles, which decay with radius -- explained by flaring of the disc. In accordance with previous work, magnetic instabilities appear to be restricted to the less-stirred outer Galactic disc. Their main effect is to create strong fields at large radii such that the radial scale length of the B-field increases from 4 kpc (for the case of a mean-field dynamo alone) to about 10 kpc in the hybrid models. There remain aspects (e.g., spiral arms, X-syaped halo fields, fluctuating fields) that are not captured by the current model and that will require further development towards a fully dynamical evolution. Nevertheless, the work presented demonstrates that a hybrid modeling of the Galactic dynamo is feasible and can serve as a foundation for future efforts.
1310.6248
The planetary system to KIC11442793: a compact analogue to the solar system
Cabrera, et al
Announce the discovery of 7 transiting planets around a Kepler target, a current record for transiting systems. Planets b, c, e and f are new; d, g, h previously reported, revise their orbital parameters and confirm their planetary nature. Planets h and g are gas giants and show strong dynamical interactions. Orbit of planet g is perturbed in such a way that its orbital period changes by 25.7h between two consecutive transits during the length of the observations (largest perturbation found so far). The rest of the planets also show mutual interactions: planets d, e and f are super-Earths close to a mean motion resonance chain (2:3:4), and planets b and c, with sizes below 2 Earth radii, are within 0.5% of the 4:5 mean motion resonance. This complex system presents some similarities to our Solar System, with small planets in inner orbits and gas giants in outer orbits. It is, however, more compact. The outer planet has an orbital distance around 1 AU, and the relative position of the gas giants is opposite to that of Jupiter and Saturn, which is closer to the expected result of planet formation theories. The dynamical interactions between planets are also much richer.
1310.6261
The link between magnetic fields and filamentary clouds: bimodal cloud orientations in the Gould belt
Li, Fang, Henning, Kainulainen
* Gould belt: a partial ring of stars in the MW, about 3k lyr across, tilted toward the galactic plane by 16-20 degrees. Conatins many O- and B-type stars, and may represent the local spiral to which the Sun belongs---currently the Sun is about 325 lyrs from the arm's center. The belt is thought to be from 30 to 50 Myrs old, and of unknown origin. Belt contains the constellations Cephus, Lactera, Perseus, Orion, Canis Major, Puppis, Vela, Carina, Crux, Centaurus, Lupus, and Scorpius (MW also passes through most of these constellations). A recent theory is that the Gould Belt formed about 30 Myrs ago when a blob of DM collided with a molecular cloud in our region. These is also evidence for similar Gould belts in other galaxies.
The orientations of filamentary molecular clouds in the Gould belt and their local ICM (inter-cloud media) B-fields are studied using NIR dust extinction maps and optical stellar polarimetry data. These filamentary clouds are few-to-ten parsecs in length, and find that their orientations tend to be either parallel or perpendicular to the mean field directions of the local ICM. This bimodal distribution is not found in cloud simulations with super-Alfvenic turbulence, in which the cloud orientations should be random. ICM B-felds that are dynamically important compared to inertial-range turbulence and self-gravity can readily explain both field-filament configurations. Previous studies commonly recognize that strong B-fields can guide gravitational contraction and result in filaments perpendicular to them, but few discuss the fact that B-fields can also channel sub-Alfvenic turbulence to form filaments aligned with them. This strong-field scenario of cloud formation is also consistent with the constant field strength observed from ICM to clouds (Crutcher+ 2010) and is possible to explain the "hub-filament" cloud structure (Myers 2009) and the density threshold of cloud gravitational contraction (Kainulainen+ 2009).
1310.6267
The high-ion content and kinematics of low-redshift Lyman limit systems
Fox et al
Study the high-ionization phase and kinematics of the circumgalactic medium around low-z galaxies using a sample of 23 Lyman limit systems (LLSs) at 0.08<z<0.93 observed with the cosmic origins spectrograph onboard HST. Lehner+ 2013 showed that low-z LLSs have a bimodal metallicity distribution. Here, extend that analysis to search for differences between the high-ion and kinematic properties of the metal-poor and metal-rich branches. Find that metal-rich LLSs tend to show higher O VI columns and broader O VI profiles than metal-poor LLSs. The total H I line width (dv90 stats) in LLSs is not correlated with metallicity, indicating that the H I kinematics alone cannot be used to distinguish inflow from outflow and gas recycling. Among the 17 LLSs with O VI detections, all but two show evidence of kinematic sub-structure, in the form of O VI-H I centroid offsets, multiple components, or both. Using various scenarios for how the metallicity in the high-ion and low-ion phases of each LLS compare, constrain the ionized hydrogen column in the O VI phase to lie in the range log N(H II)~17.6-20. The O VI phase of LLSs is a substantial baryon reservoir, with M(high-ion)~1e8.5-10.9 (R/150 kpc)^2 solar masses, similar to the mass in the low-ion phase. Accounting for the O VI phase approximately doubles the contribution of low-z LLSs to the cosmic baryon budget.
1310.6209
Toward a hybrid dynamo model for the Milky Way
Gressel, Elstner, Ziegler
MW's B-field is now modeled with an unprecedented level of detail and complexity, based on the rapidly increasing all-sky data of Faraday rotation measures and polarized synchrotron radiation. Complement this heuristic approach with a physically motivated, quantitative Galactic dynamo model: a model that allows for the evolution of the system as a whole, instead of just solving the induction equation for a fixed static disc. Building on the framework of mean-field magnetohydrodynamics and extending it to the realm of hybrid evolution, perform three-dimensional global simulations of the Galactic disc. Closure coefficients embodying the mean-field dynamo are calibrated against resolved box simulations of SN-driven interstellar turbulence. The emerging dynamo solutions comprise a mixture of dominant axisymmetric S0 mode, with even parity and a subdominant A0 mode, with odd parity. Notably, such a superposition of modes creates a strong localized vertical field on one side of the Galactic disc. Moreover, find significant radial pitch angles, which decay with radius -- explained by flaring of the disc. In accordance with previous work, magnetic instabilities appear to be restricted to the less-stirred outer Galactic disc. Their main effect is to create strong fields at large radii such that the radial scale length of the B-field increases from 4 kpc (for the case of a mean-field dynamo alone) to about 10 kpc in the hybrid models. There remain aspects (e.g., spiral arms, X-syaped halo fields, fluctuating fields) that are not captured by the current model and that will require further development towards a fully dynamical evolution. Nevertheless, the work presented demonstrates that a hybrid modeling of the Galactic dynamo is feasible and can serve as a foundation for future efforts.
1310.6248
The planetary system to KIC11442793: a compact analogue to the solar system
Cabrera, et al
Announce the discovery of 7 transiting planets around a Kepler target, a current record for transiting systems. Planets b, c, e and f are new; d, g, h previously reported, revise their orbital parameters and confirm their planetary nature. Planets h and g are gas giants and show strong dynamical interactions. Orbit of planet g is perturbed in such a way that its orbital period changes by 25.7h between two consecutive transits during the length of the observations (largest perturbation found so far). The rest of the planets also show mutual interactions: planets d, e and f are super-Earths close to a mean motion resonance chain (2:3:4), and planets b and c, with sizes below 2 Earth radii, are within 0.5% of the 4:5 mean motion resonance. This complex system presents some similarities to our Solar System, with small planets in inner orbits and gas giants in outer orbits. It is, however, more compact. The outer planet has an orbital distance around 1 AU, and the relative position of the gas giants is opposite to that of Jupiter and Saturn, which is closer to the expected result of planet formation theories. The dynamical interactions between planets are also much richer.
1310.6261
The link between magnetic fields and filamentary clouds: bimodal cloud orientations in the Gould belt
Li, Fang, Henning, Kainulainen
* Gould belt: a partial ring of stars in the MW, about 3k lyr across, tilted toward the galactic plane by 16-20 degrees. Conatins many O- and B-type stars, and may represent the local spiral to which the Sun belongs---currently the Sun is about 325 lyrs from the arm's center. The belt is thought to be from 30 to 50 Myrs old, and of unknown origin. Belt contains the constellations Cephus, Lactera, Perseus, Orion, Canis Major, Puppis, Vela, Carina, Crux, Centaurus, Lupus, and Scorpius (MW also passes through most of these constellations). A recent theory is that the Gould Belt formed about 30 Myrs ago when a blob of DM collided with a molecular cloud in our region. These is also evidence for similar Gould belts in other galaxies.
The orientations of filamentary molecular clouds in the Gould belt and their local ICM (inter-cloud media) B-fields are studied using NIR dust extinction maps and optical stellar polarimetry data. These filamentary clouds are few-to-ten parsecs in length, and find that their orientations tend to be either parallel or perpendicular to the mean field directions of the local ICM. This bimodal distribution is not found in cloud simulations with super-Alfvenic turbulence, in which the cloud orientations should be random. ICM B-felds that are dynamically important compared to inertial-range turbulence and self-gravity can readily explain both field-filament configurations. Previous studies commonly recognize that strong B-fields can guide gravitational contraction and result in filaments perpendicular to them, but few discuss the fact that B-fields can also channel sub-Alfvenic turbulence to form filaments aligned with them. This strong-field scenario of cloud formation is also consistent with the constant field strength observed from ICM to clouds (Crutcher+ 2010) and is possible to explain the "hub-filament" cloud structure (Myers 2009) and the density threshold of cloud gravitational contraction (Kainulainen+ 2009).
1310.6267
The high-ion content and kinematics of low-redshift Lyman limit systems
Fox et al
Study the high-ionization phase and kinematics of the circumgalactic medium around low-z galaxies using a sample of 23 Lyman limit systems (LLSs) at 0.08<z<0.93 observed with the cosmic origins spectrograph onboard HST. Lehner+ 2013 showed that low-z LLSs have a bimodal metallicity distribution. Here, extend that analysis to search for differences between the high-ion and kinematic properties of the metal-poor and metal-rich branches. Find that metal-rich LLSs tend to show higher O VI columns and broader O VI profiles than metal-poor LLSs. The total H I line width (dv90 stats) in LLSs is not correlated with metallicity, indicating that the H I kinematics alone cannot be used to distinguish inflow from outflow and gas recycling. Among the 17 LLSs with O VI detections, all but two show evidence of kinematic sub-structure, in the form of O VI-H I centroid offsets, multiple components, or both. Using various scenarios for how the metallicity in the high-ion and low-ion phases of each LLS compare, constrain the ionized hydrogen column in the O VI phase to lie in the range log N(H II)~17.6-20. The O VI phase of LLSs is a substantial baryon reservoir, with M(high-ion)~1e8.5-10.9 (R/150 kpc)^2 solar masses, similar to the mass in the low-ion phase. Accounting for the O VI phase approximately doubles the contribution of low-z LLSs to the cosmic baryon budget.
Thursday, October 24, 2013
Day 535
Thursday.
1310.6031
A rapidly star-forming galaxy 700 Million years after the big bang at z=7.51
Finkelstein et al
Out of several dozen z>7 candidate galaxies observed spectroscopically, only 5 have been confirmed via Lya emission. The small fraction of confirmed galaxies may indicate that the neutral fraction in the IGM rises quickly at z>6.5, as Lya is resonantly scattered by neutral gas. However, the small samples and limited depth of previous observations makes these conclusions tentative. Report here the results of a deep NIR spectroscopic survey of 43 z>6.5 galaxies. Detect only a single galaxy, confirming that some process is making Lya difficult to detect. The detected emission line at 1.0343 um is likely to be Lya emission, placing this galaxy at z=7.51, an epoch 700 Myr after BB. THis galaxy's colors are consistent with significant metal content, implying that galaxies become enriched rapidly. Measure a surprisingly high SFR of 330 Msun/yr, more than a factor of 100 greater tan seen in MW. Such a galaxy is unexpected in a survey of their size, suggesting that the early universe may harbor more intense sites of SF than expected.
1310.6037
H$\alpha$ star formation rates of $z$ > 1 galaxy clusters in the IRAC Shallow Cluster Survey
Zeimann et al
HST NIR spectroscopy of 18 galaxy clusters at 1<z<1.5 with WFC3: spectroscopically identify Ha emitters in both the cores of galaxy clusters as well as in field galaxies. Find a large cluster-to-clutser scatter in the SFR within a projected radius of 500 kpc, and many of the clusters (~60%) have significant levels of SF within a projected radius of 200 kpc. A stacking analysis reveals that dust reddening in these SF galaxies is positively correlated with stellar mass and may be higher in the field than the cluster at a fixed stellar mass. This may indicate a lower amount of gas in SF cluster galaxies than in the field population. Also, Ha equivalent widths of SF galaxies in the cluster environment are still suppressed below the level of the field. This suppression is most significant for lower mass galaxies (log M* < 10 Msun). Conclude that environmental effects are still important at 1<z<1.5 for SF galaxies in galaxy clusters with M*<1e10 Msun.
1310.6038
Sufficient observables for large scale structure in galaxy surveys
Carron, Szapudi
Beyond the linear regime, PS and higher order moments of matter field no longer capture all cosmological information encoded in density fluctuations. While NL transforms have been proposed to extract this information lost to traditional methods, the way to generalize these techniques to discrete processes was unclear; ad hoc extensions had some success. Pointed out in the past that the log transform approximates extremely well the optimal "sufficient statistics", observables that extract all information from the (continuous) matter field. Building on these results, generalize optimal transforms to discrete galaxy fields. Focus calculations on the Poisson sampling of an underlying lognormal density field. Solve and test the one-point case in detail, and sketch out the sufficient observables for the multi-point case. Present an accurate approximation to the sufficient observables in terms of the mean and spectrum of a NL transformed field. Find that the corresponding optimal NL transformation is directly related to the maximum a posteriori Bayesian reconstruction of the underlying continuous field with a lognormal prior as put forward in Kitaura+ 2010. Thus simple recipes for realizing the sufficient observables can be built on previously proposed algorithms that have been successfully implemented and tested in simulations.
1310.6039
The era of star formation in galaxy clusters
Brodwin et al
Analyze the SF proeprties of 16 IR-selected 1<z<1.5 (spec-z confirmed) from Spitzer/IRAC shallow cluster survey. Present new spectroscopic confirmation for six of these high-z clusters, 5 of which are at z>1.35. Using IR luminosities measured with deep Spitzer/MIPS observations at 24 um, along with robust optical+IRAC photometric redshifts and SED-fitted stellar masses, present the dust-obscured SF fractions, SFRs and sSFRs in these clusters as functions of redshift and projected clustercentric radius. Find that z~1.4 represents a transition redshift for the ISCS sample, with clear evidence of an unquenched era of cluster SF at earlier times. Beyond this z, the fraction of SF cluster members increases monotonically toward the cluster centers. Indeed, the sSFR in the cores of these distant clusters is consistent with field values at similar z, indicating that z>1.4 environment-dependent quenching had not yet been established in ISCS clusters. Combining these observations with complementary studies showing a rapid increase in the AGN fraction, a stochastic SFH, and a major merging episode at the same epoch in this cluster sample, suggest that the SB activity is likely merger-driven and that the subsequent quenching is due to feedback from merger-fueled AGN. The totality of the evidence suggest we are witnessing the final quenching period that brings and end to the era of SF in galaxy clusters and initiates the era of passive evolution.
1310.6040
The evolution of dust-obscured star formation activity in galaxy clusters relative to the field over the last 9 billion years
Alberts, ... Lin, ... et al
Compare the SF activity in cluster galaxies to the field from z=0.3-1.5 using Herschel SPIRE 250 um imaging. Utilize 274 clusters from IRAC Shallow Cluster Survey selected as rest-frame NIR overdensities over the 9 sq deg Bootesfield. This analysis allows us to quantify the evolution of SF in lusters over a long redshift baseline without bias against active cluster systems. Using a stacking analylsis, determine the average SFRs and sSFRs (sSFR = SFR/M*) of stellar mass-limited (M>1.3e10 Msun), statistical samples of cluster and field galaxies, probing both the SF and quiescent populations. Find a clear indication that the average SF in cluster galaxies is evolving more rapidly than in the field. Additionally, see enhanced SF above the field level at z~1.4 in the cluster outskirts (r>0.5 Mpc). These general trends in the cluster cores and outskirts are driven by the lower mass galaxies in our sample. Blue cluster galaxies have systematically lower sSFRs than blue field galaxies, but otherwise show no strong differential evolution wrt the field over the redshift range. This suggests that the cluster environments is bothe suppressing the SF in blue galaxies on long time-scales and rapidly transitioning some fraction of blue galaxies to the quiescent galaxy population on short time-scales. Argue that results are consistent with both strangulation and ram pressure stripping acting in these clusters, with merger activity occurring in the cluster outskirts.
1310.6042
The rapid decline in metallicity of damped Ly-$\alpha$ systems at $z\sim5$
Rafelski, ... Prochaska, et al
PResent evidence that the cosmological mean metallicity of neutral atomic hydrogen gas shows a sudden decrease at z>4.7 down to <Z>=-2.03pm0.10, which is 6 sigma deviant from that predicted by a linear fit to the data at lower redshifts. This measurement is made possible by the chemical abundance measurements of 8 new damped Lya (DLA) systems at z>4.7 observed with the Echellette Spectrograph and Imager on the Keck II telescope, doubling the number of measurements at z>4.7 to 16. The sudden decrease in metallicity is possibly due to the lower UV radiation field and higher density at high z increasing the neutral fraction of gas inside haloes, such as cold flows. This would result in a new population of presumably lower metallicity DLAs, with an increased contribution to the DLA population at higher z resulting in a reduced mean metallicity. While the comoving metal mass density of DLAs, rho_metals (z)_DLA, is flat out to z~4.3, there is evidence of a possible decrease at z>4.7. Such a decrease is expected, as otherwise most of the metals from SF galaxies would reside in DLAs by z~6. While the metallicity is decreasing at high z, the contribution of DLAs to the total metal budget of the universe increases with redshift, with DLAs at z~4.3 accounting for ~20% as many metals as produced by Lyman break galaxies.
1310.6044
Counter-orbiting planets were flipped over by a coplanar outer object
Li, Naoz, Kocsis, Loeb
Some massive exoplanets with close-in orbits, so-called hot Jupiters, are observed to orbit in exactly the opposite direction to the spin of their host star. True (not projected) ~180 degree misalignment cannot be well explained with previously proposed physical processes. Here, present a mechanism that can naturally lead to these counter-orbiting systems. The gravitational influence of an outer eccentric object in a coplanar orbit increases the initial eccentricity of the planet to high values. The planet's orbit then suddenly flips by ~180 degree, rolling over its major axis. The ~180 degree flip criterion and timescale are given by simple analytic expressions that depend on the initial orbital parameters. With tidal dissipation, this mechanism naturally leads to the observed counter-orbiting systems.
1310.6046
PyGFit: a tool for extracting PSF matched photometry
Mancone, Gonzalez, Moustakas, Price
PyGFit, a program designed to measure PSF-matched photometry from images with disparate pixel scales and PSF sizes. While PyGFit has a number of uses, its primary purpose is to extract robust SEDs from crowded images. It does this by fitting blended source in crowded, low resolution images with models generated from a higher resolution image. This approach minimizes the impact of crowding and also yields consistently measured fluxes in different filters, minimizing systematic uncertainty in the final SEDs. Present an example of applying PyGFit to real data and perform simulations to test its fidelity. The uncertainty in the best-fit flux rises sharply as a function of nearest-neightbor distance for objects with a neighbor within 60% of the PSF size. Similarly, the uncertainty increases quickly for objects blended with a neighbor more than four times brighter. For all other objects the fidelity of PyGFit's results depends only on flux, and the uncertainty is primarily limited by sky noise.
1310.6148
A dearth of dark matter in strong gravitational lenses
Sanders
Show that the dynamical masses of the SLACS sample of strong gravitational lenses are consistent with the stellar masses determined from population synthesis models using the Salpeter IMF. This is true in the context of both Newtonian and modified Newtonian dynamics, and is in agreement with the expectation of MOND that there should be little classical discrepancy within the high surface brightness regions probed by SL. There is also dynamical evidence from this sample supporting the claim that the mass-to-light ratio of the stellar component increases with the velocity dispersion.
1310.6175
Spherical collapse and halo mass function in the symmetron model
Taddei, Catena, Pietroni
Study the gravitational clustering of spherically symmetric overdensities and the statistics of the resulting DM haloes in the "symmetron model", in which a new long range force is mediated by a Z_2 symmetric scalar field. Depending on the initial radius of the overdensity, identify two distinct regimes: for small initial radii, the symmetron mediated force affects the spherical collapse at all redshifts; for initial radii larger than some critical size this force vanishes before collapse because of the symmetron screening mechanism. In both cases overdensities collapse earlier than in the LCDM and statistically tend to form more massive dark matter haloes. Regarding the halo-mass function of these objects, observe order one departures from standard LCDM predictions. The formalism developed here can be easily applied to other models where fifth-forces participate to the dynamics of the gravitational collapse.
1310.6031
A rapidly star-forming galaxy 700 Million years after the big bang at z=7.51
Finkelstein et al
Out of several dozen z>7 candidate galaxies observed spectroscopically, only 5 have been confirmed via Lya emission. The small fraction of confirmed galaxies may indicate that the neutral fraction in the IGM rises quickly at z>6.5, as Lya is resonantly scattered by neutral gas. However, the small samples and limited depth of previous observations makes these conclusions tentative. Report here the results of a deep NIR spectroscopic survey of 43 z>6.5 galaxies. Detect only a single galaxy, confirming that some process is making Lya difficult to detect. The detected emission line at 1.0343 um is likely to be Lya emission, placing this galaxy at z=7.51, an epoch 700 Myr after BB. THis galaxy's colors are consistent with significant metal content, implying that galaxies become enriched rapidly. Measure a surprisingly high SFR of 330 Msun/yr, more than a factor of 100 greater tan seen in MW. Such a galaxy is unexpected in a survey of their size, suggesting that the early universe may harbor more intense sites of SF than expected.
1310.6037
H$\alpha$ star formation rates of $z$ > 1 galaxy clusters in the IRAC Shallow Cluster Survey
Zeimann et al
HST NIR spectroscopy of 18 galaxy clusters at 1<z<1.5 with WFC3: spectroscopically identify Ha emitters in both the cores of galaxy clusters as well as in field galaxies. Find a large cluster-to-clutser scatter in the SFR within a projected radius of 500 kpc, and many of the clusters (~60%) have significant levels of SF within a projected radius of 200 kpc. A stacking analysis reveals that dust reddening in these SF galaxies is positively correlated with stellar mass and may be higher in the field than the cluster at a fixed stellar mass. This may indicate a lower amount of gas in SF cluster galaxies than in the field population. Also, Ha equivalent widths of SF galaxies in the cluster environment are still suppressed below the level of the field. This suppression is most significant for lower mass galaxies (log M* < 10 Msun). Conclude that environmental effects are still important at 1<z<1.5 for SF galaxies in galaxy clusters with M*<1e10 Msun.
1310.6038
Sufficient observables for large scale structure in galaxy surveys
Carron, Szapudi
Beyond the linear regime, PS and higher order moments of matter field no longer capture all cosmological information encoded in density fluctuations. While NL transforms have been proposed to extract this information lost to traditional methods, the way to generalize these techniques to discrete processes was unclear; ad hoc extensions had some success. Pointed out in the past that the log transform approximates extremely well the optimal "sufficient statistics", observables that extract all information from the (continuous) matter field. Building on these results, generalize optimal transforms to discrete galaxy fields. Focus calculations on the Poisson sampling of an underlying lognormal density field. Solve and test the one-point case in detail, and sketch out the sufficient observables for the multi-point case. Present an accurate approximation to the sufficient observables in terms of the mean and spectrum of a NL transformed field. Find that the corresponding optimal NL transformation is directly related to the maximum a posteriori Bayesian reconstruction of the underlying continuous field with a lognormal prior as put forward in Kitaura+ 2010. Thus simple recipes for realizing the sufficient observables can be built on previously proposed algorithms that have been successfully implemented and tested in simulations.
1310.6039
The era of star formation in galaxy clusters
Brodwin et al
Analyze the SF proeprties of 16 IR-selected 1<z<1.5 (spec-z confirmed) from Spitzer/IRAC shallow cluster survey. Present new spectroscopic confirmation for six of these high-z clusters, 5 of which are at z>1.35. Using IR luminosities measured with deep Spitzer/MIPS observations at 24 um, along with robust optical+IRAC photometric redshifts and SED-fitted stellar masses, present the dust-obscured SF fractions, SFRs and sSFRs in these clusters as functions of redshift and projected clustercentric radius. Find that z~1.4 represents a transition redshift for the ISCS sample, with clear evidence of an unquenched era of cluster SF at earlier times. Beyond this z, the fraction of SF cluster members increases monotonically toward the cluster centers. Indeed, the sSFR in the cores of these distant clusters is consistent with field values at similar z, indicating that z>1.4 environment-dependent quenching had not yet been established in ISCS clusters. Combining these observations with complementary studies showing a rapid increase in the AGN fraction, a stochastic SFH, and a major merging episode at the same epoch in this cluster sample, suggest that the SB activity is likely merger-driven and that the subsequent quenching is due to feedback from merger-fueled AGN. The totality of the evidence suggest we are witnessing the final quenching period that brings and end to the era of SF in galaxy clusters and initiates the era of passive evolution.
1310.6040
The evolution of dust-obscured star formation activity in galaxy clusters relative to the field over the last 9 billion years
Alberts, ... Lin, ... et al
Compare the SF activity in cluster galaxies to the field from z=0.3-1.5 using Herschel SPIRE 250 um imaging. Utilize 274 clusters from IRAC Shallow Cluster Survey selected as rest-frame NIR overdensities over the 9 sq deg Bootesfield. This analysis allows us to quantify the evolution of SF in lusters over a long redshift baseline without bias against active cluster systems. Using a stacking analylsis, determine the average SFRs and sSFRs (sSFR = SFR/M*) of stellar mass-limited (M>1.3e10 Msun), statistical samples of cluster and field galaxies, probing both the SF and quiescent populations. Find a clear indication that the average SF in cluster galaxies is evolving more rapidly than in the field. Additionally, see enhanced SF above the field level at z~1.4 in the cluster outskirts (r>0.5 Mpc). These general trends in the cluster cores and outskirts are driven by the lower mass galaxies in our sample. Blue cluster galaxies have systematically lower sSFRs than blue field galaxies, but otherwise show no strong differential evolution wrt the field over the redshift range. This suggests that the cluster environments is bothe suppressing the SF in blue galaxies on long time-scales and rapidly transitioning some fraction of blue galaxies to the quiescent galaxy population on short time-scales. Argue that results are consistent with both strangulation and ram pressure stripping acting in these clusters, with merger activity occurring in the cluster outskirts.
1310.6042
The rapid decline in metallicity of damped Ly-$\alpha$ systems at $z\sim5$
Rafelski, ... Prochaska, et al
PResent evidence that the cosmological mean metallicity of neutral atomic hydrogen gas shows a sudden decrease at z>4.7 down to <Z>=-2.03pm0.10, which is 6 sigma deviant from that predicted by a linear fit to the data at lower redshifts. This measurement is made possible by the chemical abundance measurements of 8 new damped Lya (DLA) systems at z>4.7 observed with the Echellette Spectrograph and Imager on the Keck II telescope, doubling the number of measurements at z>4.7 to 16. The sudden decrease in metallicity is possibly due to the lower UV radiation field and higher density at high z increasing the neutral fraction of gas inside haloes, such as cold flows. This would result in a new population of presumably lower metallicity DLAs, with an increased contribution to the DLA population at higher z resulting in a reduced mean metallicity. While the comoving metal mass density of DLAs, rho_metals (z)_DLA, is flat out to z~4.3, there is evidence of a possible decrease at z>4.7. Such a decrease is expected, as otherwise most of the metals from SF galaxies would reside in DLAs by z~6. While the metallicity is decreasing at high z, the contribution of DLAs to the total metal budget of the universe increases with redshift, with DLAs at z~4.3 accounting for ~20% as many metals as produced by Lyman break galaxies.
1310.6044
Counter-orbiting planets were flipped over by a coplanar outer object
Li, Naoz, Kocsis, Loeb
Some massive exoplanets with close-in orbits, so-called hot Jupiters, are observed to orbit in exactly the opposite direction to the spin of their host star. True (not projected) ~180 degree misalignment cannot be well explained with previously proposed physical processes. Here, present a mechanism that can naturally lead to these counter-orbiting systems. The gravitational influence of an outer eccentric object in a coplanar orbit increases the initial eccentricity of the planet to high values. The planet's orbit then suddenly flips by ~180 degree, rolling over its major axis. The ~180 degree flip criterion and timescale are given by simple analytic expressions that depend on the initial orbital parameters. With tidal dissipation, this mechanism naturally leads to the observed counter-orbiting systems.
1310.6046
PyGFit: a tool for extracting PSF matched photometry
Mancone, Gonzalez, Moustakas, Price
PyGFit, a program designed to measure PSF-matched photometry from images with disparate pixel scales and PSF sizes. While PyGFit has a number of uses, its primary purpose is to extract robust SEDs from crowded images. It does this by fitting blended source in crowded, low resolution images with models generated from a higher resolution image. This approach minimizes the impact of crowding and also yields consistently measured fluxes in different filters, minimizing systematic uncertainty in the final SEDs. Present an example of applying PyGFit to real data and perform simulations to test its fidelity. The uncertainty in the best-fit flux rises sharply as a function of nearest-neightbor distance for objects with a neighbor within 60% of the PSF size. Similarly, the uncertainty increases quickly for objects blended with a neighbor more than four times brighter. For all other objects the fidelity of PyGFit's results depends only on flux, and the uncertainty is primarily limited by sky noise.
1310.6148
A dearth of dark matter in strong gravitational lenses
Sanders
Show that the dynamical masses of the SLACS sample of strong gravitational lenses are consistent with the stellar masses determined from population synthesis models using the Salpeter IMF. This is true in the context of both Newtonian and modified Newtonian dynamics, and is in agreement with the expectation of MOND that there should be little classical discrepancy within the high surface brightness regions probed by SL. There is also dynamical evidence from this sample supporting the claim that the mass-to-light ratio of the stellar component increases with the velocity dispersion.
1310.6175
Spherical collapse and halo mass function in the symmetron model
Taddei, Catena, Pietroni
Study the gravitational clustering of spherically symmetric overdensities and the statistics of the resulting DM haloes in the "symmetron model", in which a new long range force is mediated by a Z_2 symmetric scalar field. Depending on the initial radius of the overdensity, identify two distinct regimes: for small initial radii, the symmetron mediated force affects the spherical collapse at all redshifts; for initial radii larger than some critical size this force vanishes before collapse because of the symmetron screening mechanism. In both cases overdensities collapse earlier than in the LCDM and statistically tend to form more massive dark matter haloes. Regarding the halo-mass function of these objects, observe order one departures from standard LCDM predictions. The formalism developed here can be easily applied to other models where fifth-forces participate to the dynamics of the gravitational collapse.
Wednesday, October 23, 2013
Day 534
Wednesday.
1310.5145
A new stellar chemo-kinematic relation reveals the merger history of the Milky Way disc
Minchev et al
Velocity dispersions of stars near the Sun are known to increase with stellar age, but age can be difficult to determine so a proxy like the abundance of alpha elements (e.g., Mg) with respect to iron, [alpha/Fe], is used. Here, report an unexpected behavior found in the velocity dispersion of a sample of giant stars in the RAVE survey with high quality chemical and kinematical information, in that it decreases strongly for stars with [Mg/Fe]>0.4 dex (i.e., those that formed in the first Gyr of the Galaxy's life). THese findings are explained by perturbations from massive mergers in the early Universe, which have affected more strongly the outer parts o the disc, and the subsequent radial migration of stars with cooler kinematics from the inner disc. Similar reversed trends in velocity dispersion are also found for different metallicity subpopulations. Results suggest that the MW disc merger history can be recovered by relating the observed chemo-kinematic relations to the properties of past merger events.
1310.5148
Star formation and AGN activity in interacting galaxies: a near-UV perspective
Scott, Kaviraj
Study nearby (<500 km/s), close (<30 kpc) galaxy pairs in SDSS to study key factors affecting SF and AGN activity triggered during galaxy interactions. GALEX UV flux used to estimate sSFRs, find a factor of ~5.3 increase in sSFR for low mass 1e8-11 Msun close pair galaxies and a factor of ~2.1 increase in sSFR for high mass (1e11-13 Msun) close pairs compared to the general galaxy population. Considering galaxies of all masses, find a factor of ~1.8 enhancement in sSFR for close pairs in field environments compared to non-pairs, with no significant increase for pairs in group and cluster environments. A modest decrease of a factor of ~1.4 is found in the Seyfert fraction in close pair galaxies when compared to isolated galaxies, which suggests that mergers may not trigger AGN activity at the close-pair stage or may trigger a different class of AGN. This becomes a factor of ~4.2 decrease when analysis is restricted to high mass close pairs in group or cluster environments.
1310.5151
Dilution in elliptical galaxies: implications for the relation between metallicity, stellar mass and star formation rate
Yates, Kauffmann
Investigate whether gradual dilution of the gas in some elliptical galaxies is the cause of a positive correlation between SFR and gas-phase metallicity (Zg) at high stellar mass (M*) in the local Universe. Two classes of massive (M*>=1e10.5 Msun) galaxy are selected by high sSFRs and high Zg, and the second class by low sSFR and low Zg. These criteria roughly distinguish disc-dominant galaxies from metal-poor, elliptical galaxies. In SAM, the second class of galaxies obtain low sSFR and low Zg due to gradual dilution of the ISM by accretion of metal-poor gas via infalling clumps and low-mass satellites. This occurs after a merger-induced SB and the associated SN feedback have quenched most of the original gas reservoir. A number of signatures of this evolution are present in these model galaxies at z=0, including low gas fractions, large central BHs, elliptical morphologies, old ages, and importantly, low (Zg-Z*) indicating dilution after SF. All of these properties are also found in low sSFR, low-Zg, massive galaxies in the SDSS-DR7. This provides strong, indirect evidence that some elliptical galaxies are undergoing gradual dilution after a gas-rich merger in the local Universe. This dilution scenario also explains the positive correlation between SFR and Zg measured in high-M* galaxies, and therefore has consequences for the local fundamental metallicity relation, which assumes a weak anti-correlation between SFR and Zg above 1e10.5 Msun.
1310.5177
The SWELLS survey. VI. hierarchical inference of the initial mass functions of bulges and discs
Brewer, Marshall, Auger, Treu, Dutton, Barnabè
"IMF is universal" being challenged: "Heavy" IMF preferred for massive early-type galaxies, while this IMF is inconsistent with the properties of less massive, later-type galaxies. These discoveries motivate the hypothesis that the IMF may vary (possibly very slightly) across galaxies and across components of individual galaxies (e.g. bulges vs disks). In this paper, use a sample of 19 late-type SL from the SWELLS survey to investigate the IMFs of the bulges and discs in late-type galaxies. Perform a joint analysis of the galaxies' total masses (constrained by SL) and stellar masses (constrained by optical and NIR colors in the context of a SPS model, up to an IMF normalization parameter). Using minimal assumptions apart form the physical constraint that the total stellar mass within any aperture must be less than the total mass within the aperture, find that the bulges of the galaxies cannot have IMFs heavier (i.e., implying high mass per unit luminosity) than Salpeter, while the disc IMFs are not well constrained by this data set. Also discuss the necessity for hierarchical modeling when combining incomplete information about multiple astronomical objects. This modeling approach allows us to place upper limits on the size of any departures from universality. More data, including spatially resolved kinematics and stellar population diagnostics over a range of bulge and disc masses, are needed to robustly quantify how the IMF varies within galaxies.
1310.5412
Transient weak-lensing by cosmological dark matter microhaloes
Rahvar, Baghram, Afshordi
Study of the time variation of the apparent flux of cosmological point sources due to the transient WL by DM microhaloes. Derive correspondence between the temporal PS of WL magnification and the spatial PS of density on small scales. Considering different approximations for the small scale structure of DM, predict the apparent magnitude of cosmological point sources to vary by as much as 1e-4 to 1e-3 due to this effect, within a period of a few months. This red photometric noise has an almost perfect gaussian statistics, to one part in ~1e4. Also compare the transient weak lensing PS with the BG effects such as the stellar microlensing on cosmological scales. A quasar lensed by a galaxy or cluster with multiple images, is a suitable system for this study as: (i) using the time-delay method between different images, can remove the intrinsic variations of the quasar, and (ii) strong lensing enhances signals from the transient WL. Also require the images to form at large angular separations from the center of the lensing structure, in order to minimize contamination by the stellar microlensing. With long-term monitoring of quasar SL systems with a 10 m class telescope, can examine the existence of dark microhaloes as the building blocks of DM structures. Failure to detect this signal may either be caused by a breakdown of CDM hierarchy on small scales, or rather interpreted as evidence against CDM paradigm, e.g. in favor of modified gravity models.
1310.5450
The origin of cold gas in giant elliptical galaxies and its role in fueling radio-mode AGN feedback
Werner et al
Eight nearby, X-ray and optically bright, giant elliptical galaxies studied in multi-wavelength. All systems with extended Ha emission (6/8) display significant [CII] line emission indicating the presence of cold gas. This emission is co-spatial with the Ha+[NII] emitting nebulae and the lowest entropy X-ray emitting plasma. The entropy profiles of the hot galactic atmospheres show a clear dichotomy, with the systems displaying extended emission line nebulae having lower entropies beyond r~1 kpc than the cold-gas-poor systems. Show that while the hot atmospheres of the cold-gas-poor galaxies are thermally stable outside of their innermost cores, the atmospheres of the cold-gas-rich systems are prone to cooling instabilities. This result indicates that the cold gas is produced chiefly by thermally unstable cooling from the hot phase. Show that cooling instabilities may develop more easily in rotating systems and discuss an alternative conditions for thermal instability for this case. The hot atmospheres of cold-gas-rich galaxies display disturbed morphologies indicating that the accretion of clumpy multiphase gas in these systems may result in variable power output of the AGN jets, potentially triggering sporadic, larger outbursts. In the two cold-gas-poor, X-ray morphologically relaxed galaxies of this sample, powerful AGN outbursts may have destroyed or removed most of the cold gas from the cores, allowing the jets to propagate and deposit most of their energy further out, increasing the entropy of the hot galactic atmospheres and leaving their cores relatively undisturbed.
1310.5486
Three-dimensional microlensing
Mao, Witt, An
Lensing where 2 lenses are located at different distances along the LoS. Formulate the lens equation in complex notations and recover several previous results. There are 4~6 images, with an equal number of images with positive and negative parities. Find that the sum of signed magnifications for six image configurations is unity. Furthermore, show that the light curves can be qualitatively different from those for binary lensing in a single plane. In particular, the magnifications between a 'U'-shaped caustic crossing can be close to unity, rather than having a minimum magnification of 3 as in the single plane binary lensing. THere is only a small probability 3-dimentionsl microlensing events will be seen in microlensing toward the Galactic centre. It is more likely they will be first seen in cosmological microlensing.
1310.5662
Snowmass cosmic frontiers 6 (CF6) working group summary --The bright side of the cosmic frontier: cosmic probes of fundamental physics
Beatty et al, Snowmass 2013
Topics addressed include ultra-high energy cosmic rays, neutrinos, gamma rays, baryogenesis, and experiments probing the fundamental nature of space-time.
1310.5702
A CANDES - 3d-HST synergy: resolved star formation patterns at 0.7<z<1.5
Wuyts, ... van Dokkum, ... Genzel, Grogin, Koekemoer, ... et al
Analyze the resolved stellar populations of 473 massive SF galaxies at 0.7<z<1.5, with multi-wavelength broad-band imaging from CANDELS and Ha surface brightness profiles at the same kiloparsec resolution from 3D-HST. Together they shed line on how the assembled stellar mass is distributed within galaxies, and where new stars are being formed. Find the Ha morphologies to resemble more closely those observed in the ACS I band than in the WFC3 H band, especially for the larger systems. Next derive a novel prescription for Ha dust corrections, which accounts for extra extinction towards HII regions. The prescription leads to consistent SFR estimates and reproduces the observed relation between the Ha/UV luminosity ratio and visual extinction, both on a pixel-by-pixel and on a galaxy-integrated level. Find the surface density of SF to correlate with the surface density of assembled stellar mass for spatially resolved regions within galaxies, akin to the so-called 'MS of SF' established on a galaxy-integrated level. Deviations from this relation towards lower equivalent widths are found in the inner regions of galaxies. Clumps and spiral features are associated with enhanced Ha equivalent widths, bluer colors, and higher sSFRs compared to the underlying disk. Their Ha/UV luminosity ratio is lower than that of the underlying disk, suggesting the ACS clump selection preferentially picks up those regions of elevated SF activity that are the least obscured by dust. Analysis emphasizes that monochromatic studies of galaxy structure can be severely limited by mass-to-light ratio variations due to dust and spatially inhomogeneous SFH.
1310.5711
X-ray bright active galactic nuclei in massive galaxy clusters II: the fraction of galaxies hosting active nuclei
Ehlert, von der Linden, Allen, Brandt, Xue, Luo, Mantz, Morris, Applegate, Kelly
Measurement of the fraction of cluster galaxies hosting X-ray bright AGN as a function of clusterc entric distance in units of r_500. Analysis employs high quality Chandra X-ray and Subaru optical imaging for 42 massive X-ray selected galaxy cluster fields spanning the redshift range of 0.2<z<0.7. In total, study involves 176 AGN with R<23 optical counterparts above 0.5-8.0 keV flux limit of 1e-14 erg/cm^2/s. When excluding central dominant galaxies from the calculation, measure a cluster-galaxy AGN fraction in the central regions of the clusters that is ~3x lower that the field value. This fraction increases with cluster centric distance before becoming consistent with the field at ~2.5 r500. Data exhibit similar radial trends to those observed for star formation and optically selected AGN in cluster member galaxies, both of which are also suppressed near cluster centers to a comparable extent. These results strongly support the idea that X-ray AGN activity and strong SF are linked through their common dependence on available reservoirs of cold gas.
1310.5712
Anomalous anisotropies of cosmic rays from turbulent magnetic fields
Ahlers
Propagation of CRs in turbulent interstellar B-fields is typically described as a spatial diffusion process. This formalism predicts only a small deviation from an isotropic CR distribution in the form of a dipole in the direction of the CR density gradient or relative BG flow. Show that the existence of a global CR dipole moment necessarily generates a spectrum of higher multipole moments in the local CR distribution. These "anomalous" anisotropies are a direct consequence of Liouville's theorem in the presence of a local turbulent B-field. Show that the predictions of this model are in excellent agreement with the observed PS of multi-TeV CRs.
1310.5721
Detection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect
Van Waerbeke, Hinshaw, Murray
Correlation between GL by LSS and the tSZ effect. Using mass map from CFHTLenS and a newly-constructued tSZ map from Planck, measure a non-zero correlation between the two maps out to one degree angular separation on the sky, with an overall significance of 6 sigma. The tSZ maps are formed in a manner that removes primary CMB fluctuations and minimizes residual contamination by galactic and extragalactic dust emission, and by CO line emission. Perform numerous test to show that meausrement is immune to these residual contaminants. The resulting correlation function is consistent with the existsence of a warm baryonic gas tracing the LSS with a bias b_gas. Given the shape of the lensing kernel, signal sensitivity peaks at z~0.4, where half a degree separation on the sky corresponds toa a physical scale of ~10 Mpc. The amplitude of the signal constrains the product (b_gas/1)(Te/1 keV)(n_e/1 m^-3)=2.01 pm 0.31 pm 0.21, at z=0. Study suggests that a substantial fraction of the "missing" baryons in the universe may reside in a low density warm plasma that traces DM.
1310.5739
Super cosmic variance from mode-coupling: a worked example
LoVerde
If the entire post-inflationary patch is large compared to our Hubble volume, even a small level of non-Gaussianity can cause statistics of the primordial curvature field in our Hubble volume to be biased by mode-coupling. Explicitly compute the variation of locally measured statistics of the primordial curvature zeta from non-Gaussian mode coupling within a specific inflationary scenario: the curvaton model with a quadratic curvaton potential. This "super cosmic variance" is calculated in two ways: (i) as a super observer who has access to the curvature perturbation field across the entire post-inflationary patch and therefore sees local statistics as biased by mode coupling and (ii) as a local observer who sees the statistics of zeta determined by the local values of quantities in their Hubble patch. The two calculations agree, and show that in the quadratic curvaton model, patch-to-patch differences in statistics of zeta can be interpreted entirely as a shift in the value of the curvaton field at freeze out. Applying the same arguments to single-field slow-roll inflation gives a simple picture of how non-Gaussian mode-coupling between the curvature perturbations on very different physical scales must vanish in the attractor limit.
1310.5825
Effects of plasma on gravitational lensing
Er, Mao
Study GL when plasma surrounds the lens: easily observable at ~100th of an arcsec when an inhomogeneous plasma distribution exists. Can use the position difference in different frequencies to estimate the density of plasma in the lens. THe magnification ratios between multiple images are mainly determined by other properties of the lens, and are only weakly affected by the plasma. Find that the SL time delay will be affected by the plasma. Estimation of the Hubble constant from the time delay in low radio frequency observation may be slightly biased due to plasma in the lens. Unfortunately, the ionosphere of the Earth strongly affects low frequency radio observations; thus ability to detect the effect depends on how well the ionosphere can be calibrated out.
1310.5926
How secret interactions can reconcile sterile neutrinos with cosmology
Hannestad, Hansen, Tram
Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. However, such neutrinos seem incompatible with cosmology because they have too large an impact on cosmic structure formation. Here, show that new interactions in the sterile neutrino sector can prevent their production in the early Universe and reconcile short baseline oscillation experiments with cosmology.
Tuesday, October 22, 2013
Day 533
Tuesday, in Rome.
1310.4832
The Andromeda optical and infrared disk survey
Sick, Courteau, Cuillandre
The survey has mapped M31 in u*g'r'i' J Ks out to R=40 kpc on CFHT. Survey designed to simultaneously resolve stars while also reproducing the surface brightness of M31, allowing study of M31's global structure in the context of both resolved stellar populations and SEDs. Calibrate photometry via mapping u*g'r'i' sky background with sky-target nodding. Maps are stable, and reveal warps in the outer M31 disk in surface brightness. The equivalent mapping in NIR uses a combination of sky-target nodding and image-to-image sky offset optimization to produce stable surface brightnesses. This study enables a detailed analysis of the systematics of SED fitting with NIR bands where asymptotic giant branch stars impose a significant, but ill-constrained, contribution to the NIR light of a galaxy. Present panchromatic surface brightness maps and initial results from the NIR resolved stellar catalog.
1310.4835
Ly{\alpha} equivalent width distribution at redsfhit z $\sim$ 4.5
Zheng, et al
Lya EWs provide clues to the physical nature of nigh-z LAEs; but measuring EW distribution of high-z narrowband selected LAEs are difficult because many sources do not have broadband photometry. Investigate possible biases in measuring the intrinsic Lya EW distribution for LAE sample at z~4.5 in the Extended Chandra Deep Field South (ECDFS). Only weak Malmquist-type bias in both the intrinsic Lya LF and the EW distribution were found. However, the observed EW distribution is severely biased if one only considers LAEs with detections in the continuum. Taking the broadband non-detections into account requires fitting the distribution of the broadband-to-narrowband ratio, which then gives a larger EW distribution scale length. Assuming an exponential-form distribution of the EW, obtain constant of W_0 = 167pm44A (uncorrected for IGM absorption of Lya). Discuss the likely range of IGM absorption effects in light of recent measurements of Lya line profiles and velocity offsets. Data consistent with Lya EW being independent of UV luminosity. Simulations also imply that broad-band images should be 0.5-1 magnitude deeper than narrowband images for an effective and reasonably complete LAE survey. Comparing with consistent measurements at other redshifts, see a strong evolution in Lya EW distribuiton with redshift which goes as a power-law form of (1+z)^xi, with xi=1.7pm0.1 if no IGM corrections are applied to the Lya line, or xi=2.2pm0.1 after applying maximal IGM-absorption correction to Lya, from z=0.3 to 6.5.
1310.4841
Swansong biospheres II: the final signs of life on terrestrial planets near the end of their habitable lifetimes
O'Malley-James et al
As the title says---it will likely consist of predominantly unicellular microorganisms due to thei ncreased hostility of environmental conditions caused by the Sun as it enters the late state of its MS evolution.
1310.4842
Dust may be more rare than expected in metal poor galaxies
Fisher et al
[Nature paper] Low-dust examples: Himiko at z=6.6, and a local galaxy I Zw 18. Report observations of dust emission from I Zw 18, estimate dust mass to be 450-1800 Msun, yielding a dust-to-stellar mass ratio of 1e-6 to 1e-5 and a dust-to-gas mass ratio 3.2-13e-6. If I Zw 18 is a reasonable analog of Himiko, then Himiko's dust mass is ~50k Msun, a factor of 100 below the current upper limit. These numbers are considerably uncertain, but if most high-z galaxies are more like Himiko than like the quasar host SDSS J114816.64+525150.3, then the prospects for detecting the gas and dust in them are much poorer than hitherto anticipated.
1310.4925
Halo/galaxy bispectrum with primordial non-Gaussianity from integrated perturbation theory (iPT)
Yokoyama, Matsubara, Taruya
Derive a formula for the halo/galaxy bispectrum on the basis of the iPT. In addition to the gravity-induced non-Gaussianity, consider the non-Gaussianity of the primordial curvature perturbations, and investigate in detail the effect of such primordial non-Gaussianity on the large-scale halo/galaxy bispectrum. In iPT, the effects of primordial non-Gaussianity are wholly encapsulated in the linear (primordial) polyspectra; systematically calculate the contributions to the large-scale behaviors arising from the three types of primordial bispectrum (local-, equilateral-, and orthogonal-types), and primordial trispectrum of the local-type non-Gaussianity. Find that the equilateral- and orthogonal-type non-Gaussianities show distinct scale-dependent behaviors which can dominate the gravity-induced non-Gaussianity at very large scales. For the local-type non-Gaussianity, higher-order loop corrections are found to give a significantly large contribution to the halo/galaxy bispectrum of the squeezed shape, and eventually dominate over the other contributions on large scales. A diagrammatic approach based on the iPT helps to systematically investigate an impact of such higher-order contributions to the large-scale halo/galaxy bispectrum.
1310.4932
Chemo-dynamical simulations of dwarf galaxy evolution
Recchi
A summary review of the state-of-the-art of chemo-dynamical numerical modelling of galaxies in general, and of dwarf galaxies in particular. Pay attention to: (i) initial conditions; (ii) the equations to solve; (iii) the SF process in galaxies; (iv) the initial mass function; (v) the chemical feedback; (vi) the mechanical feedback; (vii) the environmental effects. Additionally: key results on galactic winds in galaxies, and the fate of heavy elements, freshly synthesized after an episode of SF. Summarize the topics and physical processes, relevant for evolution of galaxies, which are not properly treated in modern simulations (in the author's opinion), and deserve more attention in the future.
1310.4944
Are ultra-long gamma-ray bursts different?
Boer, Gendre, Stratta
Discovery of numbers of gamma-ray bursts with >1000 seconds, with one case with 25k seconds, open the question on whether these bursts form a new class of sources: "ultra-long GRBs", or if they form the tail of the long GRB duration distribution. Investigate statistical properties of these GRBs and compare with the overall long burst population. Discuss differences observed in their spectral properties. Find that ultra-long GRBs are statistically different form standard long GRBs with typical burst duration <100-500 seconds, for which a Wolf Rayet star progenitor is usually invoked. Interpret this result as an indication that an alternative scenario has to be found in order to explain the ultra-long GRB extreme energetics, as well as the mass reservoir and its size that can feed the central engine for such a long time.
1310.4950
The FMOS-Cosmos survey of star-forming galaxies at z~1.6 II. the mass-metallicity relation and the dependence on star formation rate and dust extinction
Zahid et al
Investigate the relationship between stellar mass, gas-phase oxygen abundance (metallicity), SFR, and dust content of SF galaxies at z~1.6 using Subaru/FMOS spectroscopy in COSMOS. The mass-metallicity relation at z~1.6 is significantly steeper than the relation observed in the local Universe. The most massive galaxies at z~1.6 (1e11 Msun) are enriched to the level observed in massive galaxies in the local Universe. The mass-metallicity relation measured at z~1.6 supports the suggestion of an empirical upper metallicity limit that does not significantly evolve with redshift. Find an anti-correlation between metallicity and SFR of galaxies at a fixed stellar mass at z~1.6 which is similar to trends observed in the local Universe. Do not find a relation between stellar mass, metallicity and SFR that is independent of redshift; data suggest that there is redshift evolution in this relation. Examine the relation between stellar mass, metallicity and dust extinction Find that at a fixed stellar mass dustier galaxies tend to be more metal rich. From examination of the stellar masses, metallicities, SFRs and dust extinctions, conclude that stellar mass is most closely related to dust extinction.
1310.5102
A new framework for numerical simulations of structure formation
Shaller et al
Numerical cosmological simulations use "coarse-graining" methods to deal with the large number of particles whose interaction must be simulated; there is no closed system of equations for the evolution of the matter density field alone and instead it should still be discretized at each timestep. This work describes a method of solving the full 6-dimensional Vlasov-Poisson equation via a system of auxiliary Schroedinger-like equations. The complexity of problem gets shifted into the choice of the number and shape of the initial wavefunctions that should only be specified at the beginning of the computation (these wavefunctions have nothing todo with the quantum nature of the actual DM particles). Discuss different prescriptions to generate the initial wave functions from the initial conditions, and demonstrate the validity of the technique on two simple test cases. This new simulation algorithm can in principle be used on an arbitrary distribution function, enabling the simulation of warm and hot dark matter structure formation scenarios.
1310.4832
The Andromeda optical and infrared disk survey
Sick, Courteau, Cuillandre
The survey has mapped M31 in u*g'r'i' J Ks out to R=40 kpc on CFHT. Survey designed to simultaneously resolve stars while also reproducing the surface brightness of M31, allowing study of M31's global structure in the context of both resolved stellar populations and SEDs. Calibrate photometry via mapping u*g'r'i' sky background with sky-target nodding. Maps are stable, and reveal warps in the outer M31 disk in surface brightness. The equivalent mapping in NIR uses a combination of sky-target nodding and image-to-image sky offset optimization to produce stable surface brightnesses. This study enables a detailed analysis of the systematics of SED fitting with NIR bands where asymptotic giant branch stars impose a significant, but ill-constrained, contribution to the NIR light of a galaxy. Present panchromatic surface brightness maps and initial results from the NIR resolved stellar catalog.
1310.4835
Ly{\alpha} equivalent width distribution at redsfhit z $\sim$ 4.5
Zheng, et al
Lya EWs provide clues to the physical nature of nigh-z LAEs; but measuring EW distribution of high-z narrowband selected LAEs are difficult because many sources do not have broadband photometry. Investigate possible biases in measuring the intrinsic Lya EW distribution for LAE sample at z~4.5 in the Extended Chandra Deep Field South (ECDFS). Only weak Malmquist-type bias in both the intrinsic Lya LF and the EW distribution were found. However, the observed EW distribution is severely biased if one only considers LAEs with detections in the continuum. Taking the broadband non-detections into account requires fitting the distribution of the broadband-to-narrowband ratio, which then gives a larger EW distribution scale length. Assuming an exponential-form distribution of the EW, obtain constant of W_0 = 167pm44A (uncorrected for IGM absorption of Lya). Discuss the likely range of IGM absorption effects in light of recent measurements of Lya line profiles and velocity offsets. Data consistent with Lya EW being independent of UV luminosity. Simulations also imply that broad-band images should be 0.5-1 magnitude deeper than narrowband images for an effective and reasonably complete LAE survey. Comparing with consistent measurements at other redshifts, see a strong evolution in Lya EW distribuiton with redshift which goes as a power-law form of (1+z)^xi, with xi=1.7pm0.1 if no IGM corrections are applied to the Lya line, or xi=2.2pm0.1 after applying maximal IGM-absorption correction to Lya, from z=0.3 to 6.5.
1310.4841
Swansong biospheres II: the final signs of life on terrestrial planets near the end of their habitable lifetimes
O'Malley-James et al
As the title says---it will likely consist of predominantly unicellular microorganisms due to thei ncreased hostility of environmental conditions caused by the Sun as it enters the late state of its MS evolution.
1310.4842
Dust may be more rare than expected in metal poor galaxies
Fisher et al
[Nature paper] Low-dust examples: Himiko at z=6.6, and a local galaxy I Zw 18. Report observations of dust emission from I Zw 18, estimate dust mass to be 450-1800 Msun, yielding a dust-to-stellar mass ratio of 1e-6 to 1e-5 and a dust-to-gas mass ratio 3.2-13e-6. If I Zw 18 is a reasonable analog of Himiko, then Himiko's dust mass is ~50k Msun, a factor of 100 below the current upper limit. These numbers are considerably uncertain, but if most high-z galaxies are more like Himiko than like the quasar host SDSS J114816.64+525150.3, then the prospects for detecting the gas and dust in them are much poorer than hitherto anticipated.
1310.4925
Halo/galaxy bispectrum with primordial non-Gaussianity from integrated perturbation theory (iPT)
Yokoyama, Matsubara, Taruya
Derive a formula for the halo/galaxy bispectrum on the basis of the iPT. In addition to the gravity-induced non-Gaussianity, consider the non-Gaussianity of the primordial curvature perturbations, and investigate in detail the effect of such primordial non-Gaussianity on the large-scale halo/galaxy bispectrum. In iPT, the effects of primordial non-Gaussianity are wholly encapsulated in the linear (primordial) polyspectra; systematically calculate the contributions to the large-scale behaviors arising from the three types of primordial bispectrum (local-, equilateral-, and orthogonal-types), and primordial trispectrum of the local-type non-Gaussianity. Find that the equilateral- and orthogonal-type non-Gaussianities show distinct scale-dependent behaviors which can dominate the gravity-induced non-Gaussianity at very large scales. For the local-type non-Gaussianity, higher-order loop corrections are found to give a significantly large contribution to the halo/galaxy bispectrum of the squeezed shape, and eventually dominate over the other contributions on large scales. A diagrammatic approach based on the iPT helps to systematically investigate an impact of such higher-order contributions to the large-scale halo/galaxy bispectrum.
1310.4932
Chemo-dynamical simulations of dwarf galaxy evolution
Recchi
A summary review of the state-of-the-art of chemo-dynamical numerical modelling of galaxies in general, and of dwarf galaxies in particular. Pay attention to: (i) initial conditions; (ii) the equations to solve; (iii) the SF process in galaxies; (iv) the initial mass function; (v) the chemical feedback; (vi) the mechanical feedback; (vii) the environmental effects. Additionally: key results on galactic winds in galaxies, and the fate of heavy elements, freshly synthesized after an episode of SF. Summarize the topics and physical processes, relevant for evolution of galaxies, which are not properly treated in modern simulations (in the author's opinion), and deserve more attention in the future.
1310.4944
Are ultra-long gamma-ray bursts different?
Boer, Gendre, Stratta
Discovery of numbers of gamma-ray bursts with >1000 seconds, with one case with 25k seconds, open the question on whether these bursts form a new class of sources: "ultra-long GRBs", or if they form the tail of the long GRB duration distribution. Investigate statistical properties of these GRBs and compare with the overall long burst population. Discuss differences observed in their spectral properties. Find that ultra-long GRBs are statistically different form standard long GRBs with typical burst duration <100-500 seconds, for which a Wolf Rayet star progenitor is usually invoked. Interpret this result as an indication that an alternative scenario has to be found in order to explain the ultra-long GRB extreme energetics, as well as the mass reservoir and its size that can feed the central engine for such a long time.
1310.4950
The FMOS-Cosmos survey of star-forming galaxies at z~1.6 II. the mass-metallicity relation and the dependence on star formation rate and dust extinction
Zahid et al
Investigate the relationship between stellar mass, gas-phase oxygen abundance (metallicity), SFR, and dust content of SF galaxies at z~1.6 using Subaru/FMOS spectroscopy in COSMOS. The mass-metallicity relation at z~1.6 is significantly steeper than the relation observed in the local Universe. The most massive galaxies at z~1.6 (1e11 Msun) are enriched to the level observed in massive galaxies in the local Universe. The mass-metallicity relation measured at z~1.6 supports the suggestion of an empirical upper metallicity limit that does not significantly evolve with redshift. Find an anti-correlation between metallicity and SFR of galaxies at a fixed stellar mass at z~1.6 which is similar to trends observed in the local Universe. Do not find a relation between stellar mass, metallicity and SFR that is independent of redshift; data suggest that there is redshift evolution in this relation. Examine the relation between stellar mass, metallicity and dust extinction Find that at a fixed stellar mass dustier galaxies tend to be more metal rich. From examination of the stellar masses, metallicities, SFRs and dust extinctions, conclude that stellar mass is most closely related to dust extinction.
1310.5102
A new framework for numerical simulations of structure formation
Shaller et al
Numerical cosmological simulations use "coarse-graining" methods to deal with the large number of particles whose interaction must be simulated; there is no closed system of equations for the evolution of the matter density field alone and instead it should still be discretized at each timestep. This work describes a method of solving the full 6-dimensional Vlasov-Poisson equation via a system of auxiliary Schroedinger-like equations. The complexity of problem gets shifted into the choice of the number and shape of the initial wavefunctions that should only be specified at the beginning of the computation (these wavefunctions have nothing todo with the quantum nature of the actual DM particles). Discuss different prescriptions to generate the initial wave functions from the initial conditions, and demonstrate the validity of the technique on two simple test cases. This new simulation algorithm can in principle be used on an arbitrary distribution function, enabling the simulation of warm and hot dark matter structure formation scenarios.
Monday, October 21, 2013
Day 532
Monday.
1310.4824
A tidally-stripped stellar component of the Magellanic bridge
Nidever, et al
SMC stellar photometry (R=4deg, 4.2 kpc) used to study the LoS depth with red clump (RC) stars. [absolute luminosities of stars in the red clump are fairly independent of stellar composition or age, so that consequently they make good standard candles for estimating astronomical distances both within the galaxy and to nearby galaxies and clusters. from wikipedia. (only for ~2 Msun stars?)] The RC LF is affected little by young (<1 Gyr) blue-loop stars in these regions because their MS counterparts are not observed in the color-magnitude diagrams. The SMC's eastern side is found to have a large LoS depth (~23 kpc), while the western side has a much shallower depth (~10 kpc), consistent with previous photographic plate photometry results. Use a model SMC RC LF to deconvolve the observed RC magnitudes and construct the density function in distance for the fields. Three of the eastern fields show a distance bimodality with one component at the "systemic" ~67kpc SMC distance and a second component at ~55 kpc. Data are not reproduced well by the various extant Magellanic Cloud and Stream simulations. However, the models predict that the known HI Magellanic Bridge (stretching from the SMC eastward towards the LMC) has a decreasing distance with angle from the SMC and should be seen in both the gaseous and stellar components. From comparison with these models, conclude that the most likely explanation for the newly identified ~55 kpc stellar structure in the eastern SMC is a stellar counterpart of the HI Magellanic Bridge that was tidally stripped from the SMC ~200 Myr ago during a close encounter with the LMC. This discovery has important implications for microlensing surveys of the SMC.
1310.4830
Strong lens time delay challenge: I. Experimental design
Dobler, Fassnacht, Treu, Marshall, Liao, Hojjati, Linder, Rumbaugh
LSST monitoring ~1000 SL systems or multiply imaged quasars; need to assess capability to measure time delays to provide input to future feasibility studies. Time delay challenge (TDC) offered as a test. TDC0 for practice (small number of data sets); TDC1 launches Dec.1 2013, consisting of 1000 light curves, a sample designed to provide the statistical power to make meaningful statements about the sub-percent accuracy required to provide competitive DE constraints in the LSST era.
1310.4824
A tidally-stripped stellar component of the Magellanic bridge
Nidever, et al
SMC stellar photometry (R=4deg, 4.2 kpc) used to study the LoS depth with red clump (RC) stars. [absolute luminosities of stars in the red clump are fairly independent of stellar composition or age, so that consequently they make good standard candles for estimating astronomical distances both within the galaxy and to nearby galaxies and clusters. from wikipedia. (only for ~2 Msun stars?)] The RC LF is affected little by young (<1 Gyr) blue-loop stars in these regions because their MS counterparts are not observed in the color-magnitude diagrams. The SMC's eastern side is found to have a large LoS depth (~23 kpc), while the western side has a much shallower depth (~10 kpc), consistent with previous photographic plate photometry results. Use a model SMC RC LF to deconvolve the observed RC magnitudes and construct the density function in distance for the fields. Three of the eastern fields show a distance bimodality with one component at the "systemic" ~67kpc SMC distance and a second component at ~55 kpc. Data are not reproduced well by the various extant Magellanic Cloud and Stream simulations. However, the models predict that the known HI Magellanic Bridge (stretching from the SMC eastward towards the LMC) has a decreasing distance with angle from the SMC and should be seen in both the gaseous and stellar components. From comparison with these models, conclude that the most likely explanation for the newly identified ~55 kpc stellar structure in the eastern SMC is a stellar counterpart of the HI Magellanic Bridge that was tidally stripped from the SMC ~200 Myr ago during a close encounter with the LMC. This discovery has important implications for microlensing surveys of the SMC.
1310.4830
Strong lens time delay challenge: I. Experimental design
Dobler, Fassnacht, Treu, Marshall, Liao, Hojjati, Linder, Rumbaugh
LSST monitoring ~1000 SL systems or multiply imaged quasars; need to assess capability to measure time delays to provide input to future feasibility studies. Time delay challenge (TDC) offered as a test. TDC0 for practice (small number of data sets); TDC1 launches Dec.1 2013, consisting of 1000 light curves, a sample designed to provide the statistical power to make meaningful statements about the sub-percent accuracy required to provide competitive DE constraints in the LSST era.
Sunday, October 20, 2013
Day 531
Friday.
1310.4208
Kepler-like Multi-plexing for mass production of microlens parallaxes
Gould, Horne
A Kepler-like wide-field satellite in Solar orbit can get microlens parallaxes for several thousands events per year. Such a satellite would also: roughly double the number of planet detections (and mass/distance determinations); yield a trove of brown-dwarf binaries with masses, distances and (frequently) full orbits, enable new probes of the stellar mass function, identify isolated BH candidates, and more. The degraded Kepler satellite can demonstrate these capabilities and make substantial initial inroads into the science potential. Differences to the current Kepler to optimize microlens parallax capabilities would mostly reduce costs. The wide-angle approach advocated has only recenetly become superior to the old narrow-angle approach.
1310.4278
Horizon Run 3: topology as a standard ruler
Speare, Gott, Kim, Park
Estimate the accuracy in determination of the cosmological distance scale measured by topology analysis, using physically self bound cold dark matter halo distribution (associated with massive galaxies in the simulation---mock catalog similar to BOSS survey). 1.7% fractional uncertainty in angular diameter distance to z=0.6; improvement over former calibrations, and a competitive error estimate with next BAO scale techniques.
1310.4317
Probing AGN triggering mechanisms through the starburstiness of the host galaxies
Lamastra et al
Estimate the fraction of AGNs hosted by SB galaxies, as a function of AGN luminosity, assuming AGN and starburst triggered by galaxy interactions during merging. SAM AGN and SB, based on on MCMC merging trees. The predicted f_bursty increases steeply with AGN luminosity from <0.2 at L_X<1e44 ergs/ to >0.9 at L_X>1e45 erg/s over 0<z<6. Compare model with AGNs in XMM-COSMOS field at 0.3<z<2, and for QSOs in 2<z<6.5. Find preliminary indications that under conservative assumptions, half of the QSO hosts are starburst galaxies.
1310.4498
Identification of a Jet-driven supernova remnant in the small Magellanic cloud: evidence for the enhancement of bipolar explosions at low metallicity
Lopez, Castro, Slane, Ramirez-Ruiz
A SN remnant in SMC (SNR 0104-72.3) may be a result of a "prompt" SNIa based on enhanced Fe abundances and its association with a SF region; this SN remnant is thought to arise from a jet-driven bipolar core-collapse SN. This SNR is highly elliptical relative to other nearby young SNRs, suggesting a CC SN origin. Compare ejecta abundances derived from spectral fits to nucleosynthetic yields of type Ia and CC SNe, and find that the Fe, Ne and Si abundances are consistent with either a spherical CC SN of a 18-20 Msun progenitor, or an aspherical CC SN of a 25 Msun progenitor. This suggests jet-driven SNe occur frequently in the low-metallicity environment of the SMC, consistent with the observational and theoretical work on broad-line Type Ic SNe and long-duration gamma-ray bursts.
1310.4506
Constraints on long-lived remnants of neutron star binary mergers from late-time radio observations of short duration gamma-ray bursts
Metzger, Bower
Coalescence of binary NSs can sometimes produce a massive NS that is potentially stable to gravitational collapse. Such a remnant has been proposed as an explanation for the late X-ray emission observed following some short duration GRBs and as possible EM counterparts to the gravitational wave chirp. A stable NS merger remnant necessarily possesses a large rotational energy > 1e52 erg, the majority of which is ultimately deposited into the surrounding circumburst medium (CBM) at mildly relativistic velocities. Present radio observations of 7 short GRBs, some of which possessed temporally extended X-ray emission, on timescales of 1-3 years following the initial burst. No radio sources detected (upper limit ~0.3 mJy at 1.4 GHz). A basic model for the synchrotron emission from the blast wave is used to constrain the presence of a long-lived NS merger remnant in each system. Depending on the GRB, non-detections translate into upper limits on the CBM density n<3e-2 to 3e-3 particles/cm^3 required for consistency with the remnant hypothesis. Upper limits rule out a long-lived remnant in two GRB cases, but cannot rule out such a remnant in other systems due to their lower inferred CBM densities based on afterglow modeling or the lack of such constraints. Additional VLA observations in the near future could place tighter limits on the presence of merger remnants in these system. The population of long-lived NS merger remnants will also be constrained by their non-detection with upcoming radio transient surveys.
1310.4208
Kepler-like Multi-plexing for mass production of microlens parallaxes
Gould, Horne
A Kepler-like wide-field satellite in Solar orbit can get microlens parallaxes for several thousands events per year. Such a satellite would also: roughly double the number of planet detections (and mass/distance determinations); yield a trove of brown-dwarf binaries with masses, distances and (frequently) full orbits, enable new probes of the stellar mass function, identify isolated BH candidates, and more. The degraded Kepler satellite can demonstrate these capabilities and make substantial initial inroads into the science potential. Differences to the current Kepler to optimize microlens parallax capabilities would mostly reduce costs. The wide-angle approach advocated has only recenetly become superior to the old narrow-angle approach.
1310.4278
Horizon Run 3: topology as a standard ruler
Speare, Gott, Kim, Park
Estimate the accuracy in determination of the cosmological distance scale measured by topology analysis, using physically self bound cold dark matter halo distribution (associated with massive galaxies in the simulation---mock catalog similar to BOSS survey). 1.7% fractional uncertainty in angular diameter distance to z=0.6; improvement over former calibrations, and a competitive error estimate with next BAO scale techniques.
1310.4317
Probing AGN triggering mechanisms through the starburstiness of the host galaxies
Lamastra et al
Estimate the fraction of AGNs hosted by SB galaxies, as a function of AGN luminosity, assuming AGN and starburst triggered by galaxy interactions during merging. SAM AGN and SB, based on on MCMC merging trees. The predicted f_bursty increases steeply with AGN luminosity from <0.2 at L_X<1e44 ergs/ to >0.9 at L_X>1e45 erg/s over 0<z<6. Compare model with AGNs in XMM-COSMOS field at 0.3<z<2, and for QSOs in 2<z<6.5. Find preliminary indications that under conservative assumptions, half of the QSO hosts are starburst galaxies.
1310.4498
Identification of a Jet-driven supernova remnant in the small Magellanic cloud: evidence for the enhancement of bipolar explosions at low metallicity
Lopez, Castro, Slane, Ramirez-Ruiz
1310.4506
Constraints on long-lived remnants of neutron star binary mergers from late-time radio observations of short duration gamma-ray bursts
Metzger, Bower
Coalescence of binary NSs can sometimes produce a massive NS that is potentially stable to gravitational collapse. Such a remnant has been proposed as an explanation for the late X-ray emission observed following some short duration GRBs and as possible EM counterparts to the gravitational wave chirp. A stable NS merger remnant necessarily possesses a large rotational energy > 1e52 erg, the majority of which is ultimately deposited into the surrounding circumburst medium (CBM) at mildly relativistic velocities. Present radio observations of 7 short GRBs, some of which possessed temporally extended X-ray emission, on timescales of 1-3 years following the initial burst. No radio sources detected (upper limit ~0.3 mJy at 1.4 GHz). A basic model for the synchrotron emission from the blast wave is used to constrain the presence of a long-lived NS merger remnant in each system. Depending on the GRB, non-detections translate into upper limits on the CBM density n<3e-2 to 3e-3 particles/cm^3 required for consistency with the remnant hypothesis. Upper limits rule out a long-lived remnant in two GRB cases, but cannot rule out such a remnant in other systems due to their lower inferred CBM densities based on afterglow modeling or the lack of such constraints. Additional VLA observations in the near future could place tighter limits on the presence of merger remnants in these system. The population of long-lived NS merger remnants will also be constrained by their non-detection with upcoming radio transient surveys.
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