1203.0297
The Pan-STARRS1 photometric system
Tonry et al
Pan-STARRS1 survey: multi epoch, multi-color observations of sky (dec>-30 deg). Determination of g, r, i, z, y, w photometric system; based on HST Calspec spectrophotometric observations, fundamentally based on models of WD atmospheres. Byproducts: transformations to other photometric systems, instrumental sensitivity, atmospheric transmission functions. Remaining systematic errors.
1203.0301
Radiation pressure and mass ejection in rho-like states of GRS 1915+105
Neilsen, Remillard, Lee
X-ray bright flare that recurs every 50-100 seconds, but the profile and duration of the flares vary significantly. Argue: all "heartbeat" oscillations can be understood as the result of a combination of a thermal-viscous radiation pressure instability, a local Eddington limit in the disk, and a sudden, radiation-pressure-driven evaporation or ejection even in the inner accretion disk. This ejection appears to be a universal, fundamental part of the rho state.
1203.0302
Clustering fossils from the early universe
Jeong, Kamionkowski
Show how to search a galaxy or 21cm survey for the imprint of primordial scalar, vector, and tensor fields. These new fields induce local departures to an otherwise statistically isotropic 2-pt correlation function (equivalently, nontrivial 4-pt correlation functions / trispectra in Fourier space), that can be decomposed into scalar, vector, and tensor components. Write down the optical estimators for these various components, show how the sensitivity to these modes depends on the galaxy-survey parameters. New probes of parity-violating early-Universe physics also presented.
1203.0304
Identification of the IR non-thermal emission in Blazars
Massaro, D'Abrusco, Ajello, Grindlay, Smith
Blazars: gamma ray sources by non-thermal emission. WISE IR data identifies a distinct region of the [2.4]-[4.6]-[12] micron color-color diagram can separate thermal to non-thermal emission, in particular the blazer population--the WISE Blazar Strip (WBS).
1203.0306
The origin and distribution of cold gas in the halo of a MW-mass galaxy
Fernandez, Joung, Putman
AMR sim of MW-sized galaxy: study cold gas in the halo. Detected in MW and others as HI clouds; indicates on-going accretion. Compare high-res sim with observation, examine origin (simulation consistent with observation of amount, covering fraction, and spatial distribution at z=0). At z=0 th HI mass accretion rate onto the disk is 0.2 Msun/yr. Histories of 20 satellites; most of them are losing gas over 0.5>z>0; median mass loss is 3.1e-3 Msun/yr. This stripped gas is a significant component of the HI gas seen in the simulation. Filamentary material coming into the halo from the IGM at all redshifts. Most of this gas does not make it directly to the disk, but part of the gas in these structures is able to cool and form clouds. Metallicity of gas allows distinction between filamentary flows and satellite gas. Find that the form accounts for at least 25-75% of the cold gas in the halo seen at any redshift.
The Pan-STARRS1 photometric system
Tonry et al
Pan-STARRS1 survey: multi epoch, multi-color observations of sky (dec>-30 deg). Determination of g, r, i, z, y, w photometric system; based on HST Calspec spectrophotometric observations, fundamentally based on models of WD atmospheres. Byproducts: transformations to other photometric systems, instrumental sensitivity, atmospheric transmission functions. Remaining systematic errors.
1203.0301
Radiation pressure and mass ejection in rho-like states of GRS 1915+105
Neilsen, Remillard, Lee
X-ray bright flare that recurs every 50-100 seconds, but the profile and duration of the flares vary significantly. Argue: all "heartbeat" oscillations can be understood as the result of a combination of a thermal-viscous radiation pressure instability, a local Eddington limit in the disk, and a sudden, radiation-pressure-driven evaporation or ejection even in the inner accretion disk. This ejection appears to be a universal, fundamental part of the rho state.
1203.0302
Clustering fossils from the early universe
Jeong, Kamionkowski
Show how to search a galaxy or 21cm survey for the imprint of primordial scalar, vector, and tensor fields. These new fields induce local departures to an otherwise statistically isotropic 2-pt correlation function (equivalently, nontrivial 4-pt correlation functions / trispectra in Fourier space), that can be decomposed into scalar, vector, and tensor components. Write down the optical estimators for these various components, show how the sensitivity to these modes depends on the galaxy-survey parameters. New probes of parity-violating early-Universe physics also presented.
1203.0304
Identification of the IR non-thermal emission in Blazars
Massaro, D'Abrusco, Ajello, Grindlay, Smith
Blazars: gamma ray sources by non-thermal emission. WISE IR data identifies a distinct region of the [2.4]-[4.6]-[12] micron color-color diagram can separate thermal to non-thermal emission, in particular the blazer population--the WISE Blazar Strip (WBS).
1203.0306
The origin and distribution of cold gas in the halo of a MW-mass galaxy
Fernandez, Joung, Putman
AMR sim of MW-sized galaxy: study cold gas in the halo. Detected in MW and others as HI clouds; indicates on-going accretion. Compare high-res sim with observation, examine origin (simulation consistent with observation of amount, covering fraction, and spatial distribution at z=0). At z=0 th HI mass accretion rate onto the disk is 0.2 Msun/yr. Histories of 20 satellites; most of them are losing gas over 0.5>z>0; median mass loss is 3.1e-3 Msun/yr. This stripped gas is a significant component of the HI gas seen in the simulation. Filamentary material coming into the halo from the IGM at all redshifts. Most of this gas does not make it directly to the disk, but part of the gas in these structures is able to cool and form clouds. Metallicity of gas allows distinction between filamentary flows and satellite gas. Find that the form accounts for at least 25-75% of the cold gas in the halo seen at any redshift.
1203.0307
The cosmological constant problem, DE, and the landscape of string theory
Bousso
Cosmological constant problem: why is Lambda at least 60 orders of magnitude smaller than known contributions from the Standard Model of particle physics? Explain why DE is almost certainly vacuum energy. Second half: vacuum landscape of string theory leads to a multiverse in which many different 3-d vacua coexist, albeit in widely separated regions. This explains both the smallness of the observed vacuum energy and the coincidence that its magnitude is comparable to the present matter density.
1203.0308
Star formation in ram pressure stripped tails
Tonnesen, Bryan
Study impact of SF and feedback on ram pressure stripping using high-res mesh sims. Theme: "stripping is a realistic model for ISM" [stripped from what?] Find: SF does not significantly affect the rate at which stripping occurs; only has a slight impact on the density and temperature distribution of the stripped gas. Stripping acts to truncate star formation in the disk over a few 1e8 yrs, does not lead to burst of SF. SF in the huge is slightly enhanced, but the resulting change in the bulge-to-disk ratio os insignificant. Stars do form in the tail, primarily from gas that is ablated from the disk and the cools and condenses in the turbulent wake. SFR in this case is small, not significant addition to ICL. SF in the tail depends primarily on the pressure in the ICM, rather than the ram pressure strength. Compare observations of star formation in stripped tails, finding that many of the discrepancies between simulation and observed wakes can be accounted for by different ICM pressures.
1203.0309
Scaling relations of SF regions: from kpc-size clumps to HII regions
Wisnioski, Glazebrook, Blake, Poole, Green, Wyder, Martin
Properties of 8 SF regions in 3 galaxies at z~1.3 in WiggleZ survey, resolved in the OSIRIS integral field spectrograph. Avg size 1.5 kpc; avg Jeans mass 4.2e9 Msun; in total accounting for 20-30 % of the stellar mass of the discs. Theory: larger clumps will form as a result of higher disc velocity dispersions driven-up by cosmological gas accretion. It may be predicted that SF regions at high-z should not resemble SF regions locally. Despite the increased sizes and dispersions, clumps and HII regions are found to follow tight scaling relations over the range z=0-2 for size, velocity dispersion, luminosity and mass when comparing >2000 HII regions locally and 30 clumps at z>1. Discuss results in the context of the existing simulations of clump formation and evolution, with an emphasis on the processes that drive up the turbulent motions in the ISM. Results indicate the while the turbulence of discs may have important implications for the size and luminosity of regions which form within them, the same processes govern their formation from high z to the current epoch.
1203.0310
Probing the peak of the SFR density with the extragalctic background light
Raue, Meyer
EBL (the diffuse meta-galactic photo field in UV to IR) is dominated by the emission from stars in galaxies; immediately connected with the integrated SFRD. SFRD constrained using recent limits on EBL density from observations of distant sources of high and very-high energy gamma rays. Wide range of SFRD(z), metallicity, dust absorption is investigated and their impact on EBL studied. Adopt Chabrier IMF; SFRD constrained to <0.1 Msun/yr/Mpc^3 and <0.2 Msun/yr/Mpc^3 for a redshift of z~1 and 2, respectively. These limits are in tension with SFRD measurements derived from instantaneous SF tracers, in particular for z~1 where the SFRD is high. Maybe a difference in IMF.
1203.0315
On the origin of the angular momentum properties of gas and DM in galactic haloes and its implications
Sharma, Steinmetz, Bland-Hawthorn
Use non-radiative hydro-sim of merging spherical halo angular momentum (AM) properties: Universal shape of AM distribution seen in simulations generically produced as a result of mergers. Shape: excess of low AM material; cannot explain the exponential structure of disk galaxies. Resolution: spatial distribution of low AM material found to be in the center and a conical regions close to the axis of rotation. Mechanism what preferentially discards the material in the center and prevents the material along the poles from falling onto the disc is proposed as a solution. In order for 90% of haloes to host exponential discs, one has to reject at least 40% of material. DM: inside-out transfer of AM; gas: outside-in transfer (due to differences between collision less and gas dynamics). Explain the apparent high spin of DM haloes undergoing mergers and show that a criteria stricter than what is currently used would be required to detect such unrelaxed haloes. Demonstrate: misalignment of AM between gas and DM only occurs when the intrinsic spins of the merging haloes are not aligned with the orbital AM of the system.
1203.0317
Gravitational wave heating of stars and accretion disks
Li, Kocsis, Loeb
EM counterpart of GWs emitted by SMBH binary through the viscous dissipation of the GW energy in an accretion disk and stars surrounding the SMBHB. Account for suppression of the heating rate if the forcing period is shorted than the turnover time of the largest turbulent eddies. Find: viscous heating luminosity in 0.1 Msun can be significantly higher than their intrinsic luminosity. Relative brightening is small from accretion disks.
1203.0344
Candidates of Halpha emitting regions in Magellanic stream IV cloud
Yagi, Komiyama, Yoshida
Identified Halpha emitting regions in MS IV; 3 parallel filaments with 2 arcmin width and 6-30 arcmin length at 12 arcmin intervals. The mean surface brightness is 2e-19 erg/s/cm^2/arcsec^2--low surface brightness. If part of MS, then sizes are 30pc x 100 to 500 pc; filaments lie at the leading edge of a downstream cloud, which supports shock heating and its propagation model for the ionizing source. If they are local objects, Fossil Stromgren Trails of more than 2 stars is a possible interpretation, and the sizes would be 0.1pc x 0.3-1.5pc at 180 pc distance. Need more information on its distance!
* Strömgren sphere: A sphere of ionized hydrogen (H II) around a young star of spectral classes O or B. A theoretical construct which describes the UV ionized regions.
1203.0444
Spiral instabilities in N-body simulations I: emergence from noise
Sellwood
Origin of spiral patterns in galaxies, or in DM simulations--mechanism not well understood. Ampiltudes of non-axisymmetric disturbances grow in 2 distinct phases: slow growth occurs when the relative over density is below 2%, but above, the amplitude rises more rapidly. ...
1203.0486
X-ray observations of the galaxy cluster Abell 2029 to the virial radius
Walker, Fabian, Sanders, George, Tawara
Find significant anisotropies in the temperature and entropy profiles. Cold feature found (accretion event?); away from the cold feature, the thermodynamic properties are consistent with an entropy profile which rises, but less steeply than the predictions of purely gravitational hierarchical structure formation. Spherical symmetry and hydrostatic equilibrium breaks down.
1203.0517
Prospects of observing a quasar HII region during the epoch of reinoization with redshifted 21cm
Friedrich, Datta, Mellema, Iliev
Study impact of a bright quasar on the redshifted 21cm signal during EoR. Use cosmo radiative transfer sims. Are quasar capable of substantially changing the size and morphology of the HII regions they are born in? Choose stellar and quasar luminosities in a way that is favorable to seeing such an effect, but find that quasar not able to increase the size of its native HII region substantially beyond those of large HII regions produced by clustered stellar sources alone. Quasar HII regions is found to be more spherical. Investigate prospects of detecting such HIi regions in the redshifted 21cm data from LOFAR. HII regions with 25Mpc or larger have sufficiently high detection probability for 1200 hours of integration time.
1203.0558
The metallicities of low stellar mass galaxies and the scatter in the mass-metallicity relation
Zahid, Bresolin, Kewley, Coil, Dave
Quantify the metallicities of low mass galaxies by construction the most comprehensive census to date. Use SDSS and DEEP2 survey, estimate metallicities from their optical emission lines, plus two small samples using OIII 4363 line. Examine the scatter in the local mass-metallicity (MZ) relation determined from 20k SF galaxies in SDSS and show that it is larger at lower stellar masses, consistent with theoretical scatter in MZ relation from hydro sims. Determine a lower limit for the scatter in metallicities of galaxies down to stellar masses of 1e7 Msun that is only slightly smaller than the expected scatter inferred from the SDSS MZ relation and significantly larger than what is previously established in the literature. The average metallicity of SF galaxies increases with stellar mass. By examining the scatter in the SDSS MZ relation, show that this is mostly due to the lowest metallicity galaxies. THe population of low mass, metal-rich galaxies have properties which are consistent with previously identified galaxies that may be transitional objects between gas-rich dwarf irregulars and gas-poor dwarf spheroidals and ellipticals.
The cosmological constant problem, DE, and the landscape of string theory
Bousso
Cosmological constant problem: why is Lambda at least 60 orders of magnitude smaller than known contributions from the Standard Model of particle physics? Explain why DE is almost certainly vacuum energy. Second half: vacuum landscape of string theory leads to a multiverse in which many different 3-d vacua coexist, albeit in widely separated regions. This explains both the smallness of the observed vacuum energy and the coincidence that its magnitude is comparable to the present matter density.
1203.0308
Star formation in ram pressure stripped tails
Tonnesen, Bryan
Study impact of SF and feedback on ram pressure stripping using high-res mesh sims. Theme: "stripping is a realistic model for ISM" [stripped from what?] Find: SF does not significantly affect the rate at which stripping occurs; only has a slight impact on the density and temperature distribution of the stripped gas. Stripping acts to truncate star formation in the disk over a few 1e8 yrs, does not lead to burst of SF. SF in the huge is slightly enhanced, but the resulting change in the bulge-to-disk ratio os insignificant. Stars do form in the tail, primarily from gas that is ablated from the disk and the cools and condenses in the turbulent wake. SFR in this case is small, not significant addition to ICL. SF in the tail depends primarily on the pressure in the ICM, rather than the ram pressure strength. Compare observations of star formation in stripped tails, finding that many of the discrepancies between simulation and observed wakes can be accounted for by different ICM pressures.
1203.0309
Scaling relations of SF regions: from kpc-size clumps to HII regions
Wisnioski, Glazebrook, Blake, Poole, Green, Wyder, Martin
Properties of 8 SF regions in 3 galaxies at z~1.3 in WiggleZ survey, resolved in the OSIRIS integral field spectrograph. Avg size 1.5 kpc; avg Jeans mass 4.2e9 Msun; in total accounting for 20-30 % of the stellar mass of the discs. Theory: larger clumps will form as a result of higher disc velocity dispersions driven-up by cosmological gas accretion. It may be predicted that SF regions at high-z should not resemble SF regions locally. Despite the increased sizes and dispersions, clumps and HII regions are found to follow tight scaling relations over the range z=0-2 for size, velocity dispersion, luminosity and mass when comparing >2000 HII regions locally and 30 clumps at z>1. Discuss results in the context of the existing simulations of clump formation and evolution, with an emphasis on the processes that drive up the turbulent motions in the ISM. Results indicate the while the turbulence of discs may have important implications for the size and luminosity of regions which form within them, the same processes govern their formation from high z to the current epoch.
1203.0310
Probing the peak of the SFR density with the extragalctic background light
Raue, Meyer
EBL (the diffuse meta-galactic photo field in UV to IR) is dominated by the emission from stars in galaxies; immediately connected with the integrated SFRD. SFRD constrained using recent limits on EBL density from observations of distant sources of high and very-high energy gamma rays. Wide range of SFRD(z), metallicity, dust absorption is investigated and their impact on EBL studied. Adopt Chabrier IMF; SFRD constrained to <0.1 Msun/yr/Mpc^3 and <0.2 Msun/yr/Mpc^3 for a redshift of z~1 and 2, respectively. These limits are in tension with SFRD measurements derived from instantaneous SF tracers, in particular for z~1 where the SFRD is high. Maybe a difference in IMF.
1203.0315
On the origin of the angular momentum properties of gas and DM in galactic haloes and its implications
Sharma, Steinmetz, Bland-Hawthorn
Use non-radiative hydro-sim of merging spherical halo angular momentum (AM) properties: Universal shape of AM distribution seen in simulations generically produced as a result of mergers. Shape: excess of low AM material; cannot explain the exponential structure of disk galaxies. Resolution: spatial distribution of low AM material found to be in the center and a conical regions close to the axis of rotation. Mechanism what preferentially discards the material in the center and prevents the material along the poles from falling onto the disc is proposed as a solution. In order for 90% of haloes to host exponential discs, one has to reject at least 40% of material. DM: inside-out transfer of AM; gas: outside-in transfer (due to differences between collision less and gas dynamics). Explain the apparent high spin of DM haloes undergoing mergers and show that a criteria stricter than what is currently used would be required to detect such unrelaxed haloes. Demonstrate: misalignment of AM between gas and DM only occurs when the intrinsic spins of the merging haloes are not aligned with the orbital AM of the system.
1203.0317
Gravitational wave heating of stars and accretion disks
Li, Kocsis, Loeb
EM counterpart of GWs emitted by SMBH binary through the viscous dissipation of the GW energy in an accretion disk and stars surrounding the SMBHB. Account for suppression of the heating rate if the forcing period is shorted than the turnover time of the largest turbulent eddies. Find: viscous heating luminosity in 0.1 Msun can be significantly higher than their intrinsic luminosity. Relative brightening is small from accretion disks.
1203.0344
Candidates of Halpha emitting regions in Magellanic stream IV cloud
Yagi, Komiyama, Yoshida
Identified Halpha emitting regions in MS IV; 3 parallel filaments with 2 arcmin width and 6-30 arcmin length at 12 arcmin intervals. The mean surface brightness is 2e-19 erg/s/cm^2/arcsec^2--low surface brightness. If part of MS, then sizes are 30pc x 100 to 500 pc; filaments lie at the leading edge of a downstream cloud, which supports shock heating and its propagation model for the ionizing source. If they are local objects, Fossil Stromgren Trails of more than 2 stars is a possible interpretation, and the sizes would be 0.1pc x 0.3-1.5pc at 180 pc distance. Need more information on its distance!
* Strömgren sphere: A sphere of ionized hydrogen (H II) around a young star of spectral classes O or B. A theoretical construct which describes the UV ionized regions.
1203.0444
Spiral instabilities in N-body simulations I: emergence from noise
Sellwood
Origin of spiral patterns in galaxies, or in DM simulations--mechanism not well understood. Ampiltudes of non-axisymmetric disturbances grow in 2 distinct phases: slow growth occurs when the relative over density is below 2%, but above, the amplitude rises more rapidly. ...
1203.0486
X-ray observations of the galaxy cluster Abell 2029 to the virial radius
Walker, Fabian, Sanders, George, Tawara
Find significant anisotropies in the temperature and entropy profiles. Cold feature found (accretion event?); away from the cold feature, the thermodynamic properties are consistent with an entropy profile which rises, but less steeply than the predictions of purely gravitational hierarchical structure formation. Spherical symmetry and hydrostatic equilibrium breaks down.
1203.0517
Prospects of observing a quasar HII region during the epoch of reinoization with redshifted 21cm
Friedrich, Datta, Mellema, Iliev
Study impact of a bright quasar on the redshifted 21cm signal during EoR. Use cosmo radiative transfer sims. Are quasar capable of substantially changing the size and morphology of the HII regions they are born in? Choose stellar and quasar luminosities in a way that is favorable to seeing such an effect, but find that quasar not able to increase the size of its native HII region substantially beyond those of large HII regions produced by clustered stellar sources alone. Quasar HII regions is found to be more spherical. Investigate prospects of detecting such HIi regions in the redshifted 21cm data from LOFAR. HII regions with 25Mpc or larger have sufficiently high detection probability for 1200 hours of integration time.
1203.0558
The metallicities of low stellar mass galaxies and the scatter in the mass-metallicity relation
Zahid, Bresolin, Kewley, Coil, Dave
Quantify the metallicities of low mass galaxies by construction the most comprehensive census to date. Use SDSS and DEEP2 survey, estimate metallicities from their optical emission lines, plus two small samples using OIII 4363 line. Examine the scatter in the local mass-metallicity (MZ) relation determined from 20k SF galaxies in SDSS and show that it is larger at lower stellar masses, consistent with theoretical scatter in MZ relation from hydro sims. Determine a lower limit for the scatter in metallicities of galaxies down to stellar masses of 1e7 Msun that is only slightly smaller than the expected scatter inferred from the SDSS MZ relation and significantly larger than what is previously established in the literature. The average metallicity of SF galaxies increases with stellar mass. By examining the scatter in the SDSS MZ relation, show that this is mostly due to the lowest metallicity galaxies. THe population of low mass, metal-rich galaxies have properties which are consistent with previously identified galaxies that may be transitional objects between gas-rich dwarf irregulars and gas-poor dwarf spheroidals and ellipticals.
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