Monday. Friday night, a non-karaoke at Fiddlers, resolved to go back better prepared. On Saturday: bought a piano---a Yamaha Clavinova CVP. Sunday---mostly slept, tried to open an ING account.
1201.2681
Local simulations of instabilities in Relativistic Jets I: Morphology and Energetics of the current-driven instability
O'Neill, Beckwith, Begelman
Numerical investigation of current-driven instability in magnetized jets. Ensemble of local, co-moving plasma columns, in which initial radial force balance is achieved through various combinations of magnetic, pressure, and rotational forces. Examine the resulting flow morphologies and energetics to determine degree of disruption, kinetic energy amplification, NL saturation behaviours. Find: deetails of initial force balance have a pronounced effect on the resulting flow morphology. If initial magnetic field is force-free, then deformation happens, but not disruption. If balanced by pressure gradients and/or rotation against magnetic forces: tend to shred, mix and develop turbulence. In all cases, linear growth of turbulence well described analytically. ...
* I'd like to know to what physical system this is relevant to. AGN jets?
1201.2681
Local simulations of instabilities in Relativistic Jets I: Morphology and Energetics of the current-driven instability
O'Neill, Beckwith, Begelman
Numerical investigation of current-driven instability in magnetized jets. Ensemble of local, co-moving plasma columns, in which initial radial force balance is achieved through various combinations of magnetic, pressure, and rotational forces. Examine the resulting flow morphologies and energetics to determine degree of disruption, kinetic energy amplification, NL saturation behaviours. Find: deetails of initial force balance have a pronounced effect on the resulting flow morphology. If initial magnetic field is force-free, then deformation happens, but not disruption. If balanced by pressure gradients and/or rotation against magnetic forces: tend to shred, mix and develop turbulence. In all cases, linear growth of turbulence well described analytically. ...
* I'd like to know to what physical system this is relevant to. AGN jets?
1201.2683
Constraints on light hidden sector gauge bosons from SNe cooling
Dent, Ferrer, Krauss
Derive new bound on hidden sector gauge bosons which could produce new energy loss mechanisms in SNe, enlarging the excluded region in mass-coupling space by a significant factor compared to earlier estimates. ... A significant BG of such gauge bosons may also be produced due to the cumulative effects of all SNe over cosmic history.
* a SNe (lightcurve?) can probe "hidden sector gauge bosons", but it doesn't say how.
1201.2687
Nomads of the Galaxy
Etrigari, Barnabe, Marshall, Blandford
Estimate that there may be up to 1e5 compact objects in the mass range 1e-8~10e-2 Msun per main sequence star that are unbound to a host star in the Galaxy ("nomads", "free-floating" or "rogue" planets), according to a smooth extrapolation of the mass function of unbound objects above the Jupiter-mass scale, the stellar mass density limit [?], and the metallicity of the interstellar medium. Analyze the prospects for detecting nomads via Galactic microlensing. WFIRST will measure number of nomads per main sequence star with M > M_J to ~13%, and the corresponding number for M>M_Mars to ~25%. All-sky surveys such as GAIA and LSST can identify nomads greater than about the mass of Jupiter. Suggest a dedicated drift scanning telescope that covers approximately 100 sq deg. in the Southern hemisphere: could identify nomads as small as 1e-8 Msun via microlensing of bright stars with characteristic lightcurve timescales of few seconds.
1201.2691
Search for DM satellites using the FERMI-LAT
The Fermi LAT collaboration
Find no viable Galactic DM satellite candidates from one year of data, assuming gamma-ray spectra consistent with WIMP annihilation through the bb channel.
1201.2695
On the formation of very metal-poor stars: The case of SDSS J1029151+172927
Klessen, Glober, Clark
Based on simple thermodynamic considerations, argue that the extremely metal poor star was more likely formed as a result of dust continuum cooling rather than cooling by metal lines. Conclude that the masses of extremely metal-poor stars are determined by dust-induced fragmentation.
1201.2697
UV to FIR catalogue of a galaxy sample in nearby clusters: SEDs and environmental trends
Hernandez-Fernendez, Iglesias-Paramo, Vilchez
Sample of cluster galaxies to study environmental influence on the SF activity. Clusters follow the general X-ray luminosity vs. velocity dispersion trend of L_x/sigma_c^4.4. Analysis of the distributions of galaxy density counting up to the 5th nearest neighbor Sigma_5 shows: (1) virial regions and the cluster outskirts share a common range in the high density part of the distribution, attributed to the presence of massive galaxy structures in the surroundings of virial regions. (2) Virial regions of massive clusters (sigma_c>550 km/s) present a sigma_5 distribution statistically distinguishable from the commresponding distribution of lowmass clusters: Both massive and low-mass clusters follow a similar density-radius trend, but the low-mass clusters avoid the high density extreme. Illustrate with Abell 1185 the environmental trends of galaxy populations. Low-luminosity SF galaxies appear distributed along more spread structures than their giant counterparts, whereas low-luminosity passive galaxies avoid the low-density environment. Giant passive and star-forming galaxies share rather similar sky regions with passive galaxies exhibiting more concentrated distributions.
* galaxy distribution in a cluster by SF-type.
Constraints on light hidden sector gauge bosons from SNe cooling
Dent, Ferrer, Krauss
Derive new bound on hidden sector gauge bosons which could produce new energy loss mechanisms in SNe, enlarging the excluded region in mass-coupling space by a significant factor compared to earlier estimates. ... A significant BG of such gauge bosons may also be produced due to the cumulative effects of all SNe over cosmic history.
* a SNe (lightcurve?) can probe "hidden sector gauge bosons", but it doesn't say how.
1201.2687
Nomads of the Galaxy
Etrigari, Barnabe, Marshall, Blandford
Estimate that there may be up to 1e5 compact objects in the mass range 1e-8~10e-2 Msun per main sequence star that are unbound to a host star in the Galaxy ("nomads", "free-floating" or "rogue" planets), according to a smooth extrapolation of the mass function of unbound objects above the Jupiter-mass scale, the stellar mass density limit [?], and the metallicity of the interstellar medium. Analyze the prospects for detecting nomads via Galactic microlensing. WFIRST will measure number of nomads per main sequence star with M > M_J to ~13%, and the corresponding number for M>M_Mars to ~25%. All-sky surveys such as GAIA and LSST can identify nomads greater than about the mass of Jupiter. Suggest a dedicated drift scanning telescope that covers approximately 100 sq deg. in the Southern hemisphere: could identify nomads as small as 1e-8 Msun via microlensing of bright stars with characteristic lightcurve timescales of few seconds.
1201.2691
Search for DM satellites using the FERMI-LAT
The Fermi LAT collaboration
Find no viable Galactic DM satellite candidates from one year of data, assuming gamma-ray spectra consistent with WIMP annihilation through the bb channel.
1201.2695
On the formation of very metal-poor stars: The case of SDSS J1029151+172927
Klessen, Glober, Clark
Based on simple thermodynamic considerations, argue that the extremely metal poor star was more likely formed as a result of dust continuum cooling rather than cooling by metal lines. Conclude that the masses of extremely metal-poor stars are determined by dust-induced fragmentation.
1201.2697
UV to FIR catalogue of a galaxy sample in nearby clusters: SEDs and environmental trends
Hernandez-Fernendez, Iglesias-Paramo, Vilchez
Sample of cluster galaxies to study environmental influence on the SF activity. Clusters follow the general X-ray luminosity vs. velocity dispersion trend of L_x/sigma_c^4.4. Analysis of the distributions of galaxy density counting up to the 5th nearest neighbor Sigma_5 shows: (1) virial regions and the cluster outskirts share a common range in the high density part of the distribution, attributed to the presence of massive galaxy structures in the surroundings of virial regions. (2) Virial regions of massive clusters (sigma_c>550 km/s) present a sigma_5 distribution statistically distinguishable from the commresponding distribution of lowmass clusters: Both massive and low-mass clusters follow a similar density-radius trend, but the low-mass clusters avoid the high density extreme. Illustrate with Abell 1185 the environmental trends of galaxy populations. Low-luminosity SF galaxies appear distributed along more spread structures than their giant counterparts, whereas low-luminosity passive galaxies avoid the low-density environment. Giant passive and star-forming galaxies share rather similar sky regions with passive galaxies exhibiting more concentrated distributions.
* galaxy distribution in a cluster by SF-type.
1201.2720
Testing distance estimators with the Fundamental Manifold
Zaritsky, Zabludoff, Gonzalez
FM can be used to cross-calibrate distance estimators (SN Ia, Cepheids, surface brightness fluctuations, RGB tip luminosity, circumnuclear masers, eclipsing binaries, RR Lyrae stars, and planetary nebulae luminosity functions). Find no significant discrepancies between distance methods (although ~10% level difference cannot yet be ruled out). Potential exists for significant refinement with homogeneous, near-IR magnitudes (have used B-band magnitudes). Use FM distances to (1) revisit the question of the metallicity sensitivity of various estimators, confirming the dependence of SNIa distances on host galaxy metallicity, and (2) provide an alternative calibration of H_0 that replaces the classical ladder approach in the use of extragalactic distance estimators with one that utilizes data over a wide range of distances simultaneously.
* interesting, but the accuracy is hard to guarantee with FM, unless one has absolute confidence in it.
1201.2727
Galaxy alignments in very x-ray luminous clusters as z>0.5
Hung, Ebeling
12 galaxy clusters at z>0.5, statistically complete subset of the very x-ray luminous clusters of MACS. Use HST images, find not radial galaxy slignments within 500 kpc of the cluster centers for a sample of 545 spectrscopically confirmed cluster members. A mild but insignificat trend favoring radial alignments observed within 200 kpc, and traced to galaxies on the cluster red sequence. At z~0.1, highly significant radial alignments exists, out to at least half the virial radius, based on SDSS. Why the difference? Conclude that most likely: dramatic evolution of alignment with redshift, or the presence of systematic biases in the analysis of SDSS imaging data that cause at least partly spurious alignment signals.
1201.2751
Feedback effects on low-mass star formation
Hansen, Klein, McKee, Fisher
Radiation and bipolar outflows of protostellar feedback dramatically affects the fragmentation and mass accretion from SF cores. Use ORION, and adaptic mesh refinement gravito-radiation-hydrodynamics code, to simulate the formation of cluster of low-mass stars, including both radiative transfer and protostellar outflows. Radiation feedback suppresses fragmentation, outflows reduce protostellar mass and accretion rates each by a factor of 3, reducing protostellar luminosities by an order of magnitude. Initial fragmentation at half the global Jeans length, ~0.1pc. Cores fragment repeatedly (without sufficient protostellar radiation), forming typically 10 stars each. In the absence of magnetic fields, protostellar outflows do not significantly affect the overall cloud dynamics, because of their small opening angles and poor coupling to the dense gas, resulting in a core-to-star efficiency of ~1/3. Simulation can reproduce observed core mass functions, but are sensitive to telescope resolution. Simulation with both radiation and outflow reproduces the galactic IMF and the 2-pt correlation function of the cores observed in rho Oph.
1201.2762
The dust scaling relations of the Herschel reference survey
Cortese, et al
Dust-to-stellar mass ratio anti-correlates with stellar mass, stellar mass surface density, and NUV-r colour across the whole range of parameters. Dust-to-stellar mass ratio decreases significantly when moving from late-to early-type galaxies, similarly to HI gas-fraction, supporting the idea that the cold dust is tightly coupled to the cold atomic gas component in the interstellar medium. Find a weak increase of dust-to-HI mass ratio with stellar mass and colour, but no trend seen with stellar surface mass density. Evidence for dust being removed from the SF disk of cluster galaxies, but the effect of the environment is less strong that what is observed in the case of the HI disk. Such effects naturally arise if the dust disk is less extended than the HI and follows more closely the distribution of the molecular gas phase.
1201.2849
Combining and comparing astrometric data from different epochs: a case study with Hipparcos and Nano-JASMINE
Michalik, Lindegren, Hobbs, Lammers, Yamada
Combine Hipparcos and simulated Nano-JASMINE data in a joint solution, showing significant improvement over the conventional catalogue combination.
1201.2908
A bright z=5.2 lensed submillimeter galaxy in the field of Abell 773: HLSJ091828.6+514223
Combes, Rex, Rawle, Egami, ..., Kneib, Okabe, ... et al
Found a strongly lensed submillimeter galaxy (SMB) at z=5.2429 behind Abell 773, a cluster at z=0.22. Dominant lens is a z=0.63 galaxy, not the cluster itself. Redshift identification through CO lines with IRAM-30m and EVLA. All lines decompose in a wide and strong red component, and a narrower and weaker blue component, 540 km/s apart. H2 mass derived, 1/3 contained in a cool component. Cl line shows similar abundance as other ULIRGs. Detect water line, suggesting a strong local FIR radiation field, possibly from an AGN component. Water line strong only in the red velocity component. High-z NII line detected, showing blue and red components, with a strikingly borad blue one, suggesting strong ionized gas flows.
1201.2913
The standardizability of SNIa in the NIR: evidence for a peak luminosity-decline rate relation in the near IR
Kattner, et al
Applying a correction to SNIa peak luminosities for decline rate is beneficial in the J and H bands to make SNIa more precise distance indicators (only marginal importance in the Y).
1201.2916
Reorienting our perspective or BAL quasars
DiPompeo, Brotherton, De Breuck, Laurent-Muehleisen
Multi-frequency radio observations of radio-selected BAL quasars, along with matched sample of normal quasars, presented. Measure radio spectral index from 4.9 and 8.4 GHz. Significant difference in the spectral index distributions of BAL vs non-AL quasars, with BAL sources showing an overabundance of steep-spectrum sources. Suggests that BAL are more likely to be seen farther from the radio jet axis (more observation necessary to explain the width of distribution). Relationships with spectral index and viewing angle simulated to quantify the viewing angle, find difference in the distributions of spectral index explained by allowing the BAL sources to have viewing angles extending about 10 degrees farther from the jet axis than non-BAL quasars.
Testing distance estimators with the Fundamental Manifold
Zaritsky, Zabludoff, Gonzalez
FM can be used to cross-calibrate distance estimators (SN Ia, Cepheids, surface brightness fluctuations, RGB tip luminosity, circumnuclear masers, eclipsing binaries, RR Lyrae stars, and planetary nebulae luminosity functions). Find no significant discrepancies between distance methods (although ~10% level difference cannot yet be ruled out). Potential exists for significant refinement with homogeneous, near-IR magnitudes (have used B-band magnitudes). Use FM distances to (1) revisit the question of the metallicity sensitivity of various estimators, confirming the dependence of SNIa distances on host galaxy metallicity, and (2) provide an alternative calibration of H_0 that replaces the classical ladder approach in the use of extragalactic distance estimators with one that utilizes data over a wide range of distances simultaneously.
* interesting, but the accuracy is hard to guarantee with FM, unless one has absolute confidence in it.
1201.2727
Galaxy alignments in very x-ray luminous clusters as z>0.5
Hung, Ebeling
12 galaxy clusters at z>0.5, statistically complete subset of the very x-ray luminous clusters of MACS. Use HST images, find not radial galaxy slignments within 500 kpc of the cluster centers for a sample of 545 spectrscopically confirmed cluster members. A mild but insignificat trend favoring radial alignments observed within 200 kpc, and traced to galaxies on the cluster red sequence. At z~0.1, highly significant radial alignments exists, out to at least half the virial radius, based on SDSS. Why the difference? Conclude that most likely: dramatic evolution of alignment with redshift, or the presence of systematic biases in the analysis of SDSS imaging data that cause at least partly spurious alignment signals.
1201.2751
Feedback effects on low-mass star formation
Hansen, Klein, McKee, Fisher
Radiation and bipolar outflows of protostellar feedback dramatically affects the fragmentation and mass accretion from SF cores. Use ORION, and adaptic mesh refinement gravito-radiation-hydrodynamics code, to simulate the formation of cluster of low-mass stars, including both radiative transfer and protostellar outflows. Radiation feedback suppresses fragmentation, outflows reduce protostellar mass and accretion rates each by a factor of 3, reducing protostellar luminosities by an order of magnitude. Initial fragmentation at half the global Jeans length, ~0.1pc. Cores fragment repeatedly (without sufficient protostellar radiation), forming typically 10 stars each. In the absence of magnetic fields, protostellar outflows do not significantly affect the overall cloud dynamics, because of their small opening angles and poor coupling to the dense gas, resulting in a core-to-star efficiency of ~1/3. Simulation can reproduce observed core mass functions, but are sensitive to telescope resolution. Simulation with both radiation and outflow reproduces the galactic IMF and the 2-pt correlation function of the cores observed in rho Oph.
1201.2762
The dust scaling relations of the Herschel reference survey
Cortese, et al
Dust-to-stellar mass ratio anti-correlates with stellar mass, stellar mass surface density, and NUV-r colour across the whole range of parameters. Dust-to-stellar mass ratio decreases significantly when moving from late-to early-type galaxies, similarly to HI gas-fraction, supporting the idea that the cold dust is tightly coupled to the cold atomic gas component in the interstellar medium. Find a weak increase of dust-to-HI mass ratio with stellar mass and colour, but no trend seen with stellar surface mass density. Evidence for dust being removed from the SF disk of cluster galaxies, but the effect of the environment is less strong that what is observed in the case of the HI disk. Such effects naturally arise if the dust disk is less extended than the HI and follows more closely the distribution of the molecular gas phase.
1201.2849
Combining and comparing astrometric data from different epochs: a case study with Hipparcos and Nano-JASMINE
Michalik, Lindegren, Hobbs, Lammers, Yamada
Combine Hipparcos and simulated Nano-JASMINE data in a joint solution, showing significant improvement over the conventional catalogue combination.
1201.2908
A bright z=5.2 lensed submillimeter galaxy in the field of Abell 773: HLSJ091828.6+514223
Combes, Rex, Rawle, Egami, ..., Kneib, Okabe, ... et al
Found a strongly lensed submillimeter galaxy (SMB) at z=5.2429 behind Abell 773, a cluster at z=0.22. Dominant lens is a z=0.63 galaxy, not the cluster itself. Redshift identification through CO lines with IRAM-30m and EVLA. All lines decompose in a wide and strong red component, and a narrower and weaker blue component, 540 km/s apart. H2 mass derived, 1/3 contained in a cool component. Cl line shows similar abundance as other ULIRGs. Detect water line, suggesting a strong local FIR radiation field, possibly from an AGN component. Water line strong only in the red velocity component. High-z NII line detected, showing blue and red components, with a strikingly borad blue one, suggesting strong ionized gas flows.
1201.2913
The standardizability of SNIa in the NIR: evidence for a peak luminosity-decline rate relation in the near IR
Kattner, et al
Applying a correction to SNIa peak luminosities for decline rate is beneficial in the J and H bands to make SNIa more precise distance indicators (only marginal importance in the Y).
1201.2916
Reorienting our perspective or BAL quasars
DiPompeo, Brotherton, De Breuck, Laurent-Muehleisen
Multi-frequency radio observations of radio-selected BAL quasars, along with matched sample of normal quasars, presented. Measure radio spectral index from 4.9 and 8.4 GHz. Significant difference in the spectral index distributions of BAL vs non-AL quasars, with BAL sources showing an overabundance of steep-spectrum sources. Suggests that BAL are more likely to be seen farther from the radio jet axis (more observation necessary to explain the width of distribution). Relationships with spectral index and viewing angle simulated to quantify the viewing angle, find difference in the distributions of spectral index explained by allowing the BAL sources to have viewing angles extending about 10 degrees farther from the jet axis than non-BAL quasars.
No comments:
Post a Comment