Thursday.
1209.4078
Testing the Copernican principle by constraining spatial homogeneity
Valkenburg, Marra, Clarkson
Include DE in the Copernical principle, current observations place reasonably tight constraints on possible late-time violations of the Copernican principle. Possible radial inhomogeneity marginalized over to obtain constraints of cosmological constant.
1209.4079
On the true shape of the upper end of the stellar initial mass function: the case of R136
Banerjee, Kroupa
IMF of star cluster near upper mass limit: determines the high mass stellar content, and hence the dynamics of the cluster. ... If ejection of massive stars is efficient, then the true IMF is more top-heavy than the observed one.
1209.4080
Warm-hot gas in groups and galaxies toward H2356-309
Williams, Mulchaey, Kollmeier
Three X-ray absorption line systems in the quasar spectra. Trace 1e5-7 K gas, Could be WHIM (the low-z "missing baryons") or linked to galaxies, groups, in filaments. Observations with spectroscopy show they all nominally lie within the virial radii of nearby galaxies and/or groups, and could arise in these virialized structures rather than (or in addition to) the WHIM. A fourth system doesn't seem to have a galaxy associated with it. Conclude that most X-ray absorbers are coincident with galaxy and/or group environments, though some could still trace the large-scale filamentary WHIM gas predicted by simulations.
Recent Suzaku X-ray measurements show gas mass fraction f_gas appear to be considerably larger than the cosmic mean at the virial radius R200, questioning the accuracy of the cosmological parameter estimations. Use a large suite of cosmological hydrodynamical simulations to study biases of f_gas. Compute mass profiles, find anisotropic gas and total mass distributions that imply an angular variance of f_gas at the level of 30%. This anisotropic distribution originates from the recent formation epoch of clusters, and from the strong internal baryon-to-dark-matter density bias.
1209.4084
Quenching star formation at intermediate redshifts: downsizing of the mass flux density in the green valley
Goncalves, Martin, Menendez-Delmestre, Wyder, Koekemoer
Clear bimodality indicates transition from blue to red must be a rapid process. Study >100 green valley galaxies at z~0.8, with DEIMOS spectroscopy. Infer SFH and measure stellar mass flux density transiting from blue to red when the universe was half its current age. Results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. Another aspect of downsizing: mass flux density moving towards smaller galaxies in recent times.
1209.4086
Evolutionary paths among different red galaxy types at 0.3<z<1.5 and the late buildup of massive E-S0's through major mergers
Report observational evidence of the existence of dominant evolutionary path among massive red galaxies at 0.6<z<1.5, consisting in the conversion of ire. disks into irr. spheroids, and of these ones into regular spheroids. This result implies that (1) massive red regular galaxies at low z derive from the irregular ones populating the red sequence at z~1.5, (2) progenitors of the bulk of present-day massive red regular galaxies have been blue disks that have migrated to the red sequence mostly through major mergers at 0.6<z<1.2, and (3) the formation of E-S0's that end up with M*>1e11Msun at z=0 through gas-rich major mergers has frozen since z~0.6. All these support that major mergers have played the dominant role in the definitive buildup of present-day E-S0's with M*>1e11 Msun at 0.6<z<1.2, in good agreement with hierarchical scenarios of galaxy formation.
1209.4097
Pulsations in short GRBs from black hole-neutron star mergers
Stone, Loeb, Berger
SGRBs: its origins? Observations suggest merger of binary compact object system, but unclear how to distinguish between binary neutron star progenitor and a black hole-neutron star progenitor. Quasi-periodic signal of jet precession as an observational signature of SGRBs originating in mixed binary systems, and quantify fraction of mixed binaries capable of producing SGRBs.
1209.4098
Colors of extreme exoEarth environments
Hegde, Kaltenegger
Explore potentially detectable surface features on rocky exoplanets and their connection to and importance as a habitat for extremophiles. Look for clear atmospheres on rocky planets.
1209.4141
The history of star formation in galaxies
Brown, Postman, Calzetti
NASA white paper. How and when galaxies assemble their stellar populations? How does this assembly vary with environment? It's hierarchical, but insight of assembly comes from trying to reconstruct the galaxy's SFH, chemical evolution, and kinematics. Need multi-band photometry that reach Lsun MS stars. HST can obtain such data for local group galaxies.
1209.4143
THe impacts of ultraviolet radiation feedback on galaxies during the epoch of reoinisation
Hasegawa, Semelin
During EoR, in simulations find that SF is significantly suppressed due to internal UV and SN feedback. In low mass galaxies with M<1e9 Msun, a large amount of gas is evacuated by photo-evaporation, results in the suppression of SF. SF in massive haloes also strongly suppressed despite the fact that these haloes hardly lose any gas---mainly caused by (i) small scale clumpy structures are smoothed by internal feedback, and (ii) dense gas in the galaxies mostly neutral, but H2 formation and cooling disturbed by mild photo-heating. Consistent with observations at z=6-7.
1209.4305
Star-formation laws in extreme starbursts
Garcia-Burillo, Usero, Alonso-Herrero
SFE of dense molecular gas (from FIR/HCN ratio) is factor 3-4 higher in extreme starbursts compared to normal galaxies. Duality on the Kennicutt-Schmidt laws. ...
1209.4078
Testing the Copernican principle by constraining spatial homogeneity
Valkenburg, Marra, Clarkson
Include DE in the Copernical principle, current observations place reasonably tight constraints on possible late-time violations of the Copernican principle. Possible radial inhomogeneity marginalized over to obtain constraints of cosmological constant.
1209.4079
On the true shape of the upper end of the stellar initial mass function: the case of R136
Banerjee, Kroupa
IMF of star cluster near upper mass limit: determines the high mass stellar content, and hence the dynamics of the cluster. ... If ejection of massive stars is efficient, then the true IMF is more top-heavy than the observed one.
1209.4080
Warm-hot gas in groups and galaxies toward H2356-309
Williams, Mulchaey, Kollmeier
Three X-ray absorption line systems in the quasar spectra. Trace 1e5-7 K gas, Could be WHIM (the low-z "missing baryons") or linked to galaxies, groups, in filaments. Observations with spectroscopy show they all nominally lie within the virial radii of nearby galaxies and/or groups, and could arise in these virialized structures rather than (or in addition to) the WHIM. A fourth system doesn't seem to have a galaxy associated with it. Conclude that most X-ray absorbers are coincident with galaxy and/or group environments, though some could still trace the large-scale filamentary WHIM gas predicted by simulations.
Recent Suzaku X-ray measurements show gas mass fraction f_gas appear to be considerably larger than the cosmic mean at the virial radius R200, questioning the accuracy of the cosmological parameter estimations. Use a large suite of cosmological hydrodynamical simulations to study biases of f_gas. Compute mass profiles, find anisotropic gas and total mass distributions that imply an angular variance of f_gas at the level of 30%. This anisotropic distribution originates from the recent formation epoch of clusters, and from the strong internal baryon-to-dark-matter density bias.
1209.4084
Quenching star formation at intermediate redshifts: downsizing of the mass flux density in the green valley
Goncalves, Martin, Menendez-Delmestre, Wyder, Koekemoer
Clear bimodality indicates transition from blue to red must be a rapid process. Study >100 green valley galaxies at z~0.8, with DEIMOS spectroscopy. Infer SFH and measure stellar mass flux density transiting from blue to red when the universe was half its current age. Results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. Another aspect of downsizing: mass flux density moving towards smaller galaxies in recent times.
1209.4086
Evolutionary paths among different red galaxy types at 0.3<z<1.5 and the late buildup of massive E-S0's through major mergers
Report observational evidence of the existence of dominant evolutionary path among massive red galaxies at 0.6<z<1.5, consisting in the conversion of ire. disks into irr. spheroids, and of these ones into regular spheroids. This result implies that (1) massive red regular galaxies at low z derive from the irregular ones populating the red sequence at z~1.5, (2) progenitors of the bulk of present-day massive red regular galaxies have been blue disks that have migrated to the red sequence mostly through major mergers at 0.6<z<1.2, and (3) the formation of E-S0's that end up with M*>1e11Msun at z=0 through gas-rich major mergers has frozen since z~0.6. All these support that major mergers have played the dominant role in the definitive buildup of present-day E-S0's with M*>1e11 Msun at 0.6<z<1.2, in good agreement with hierarchical scenarios of galaxy formation.
1209.4097
Pulsations in short GRBs from black hole-neutron star mergers
Stone, Loeb, Berger
SGRBs: its origins? Observations suggest merger of binary compact object system, but unclear how to distinguish between binary neutron star progenitor and a black hole-neutron star progenitor. Quasi-periodic signal of jet precession as an observational signature of SGRBs originating in mixed binary systems, and quantify fraction of mixed binaries capable of producing SGRBs.
1209.4098
Colors of extreme exoEarth environments
Hegde, Kaltenegger
Explore potentially detectable surface features on rocky exoplanets and their connection to and importance as a habitat for extremophiles. Look for clear atmospheres on rocky planets.
1209.4141
The history of star formation in galaxies
Brown, Postman, Calzetti
NASA white paper. How and when galaxies assemble their stellar populations? How does this assembly vary with environment? It's hierarchical, but insight of assembly comes from trying to reconstruct the galaxy's SFH, chemical evolution, and kinematics. Need multi-band photometry that reach Lsun MS stars. HST can obtain such data for local group galaxies.
1209.4143
THe impacts of ultraviolet radiation feedback on galaxies during the epoch of reoinisation
Hasegawa, Semelin
During EoR, in simulations find that SF is significantly suppressed due to internal UV and SN feedback. In low mass galaxies with M<1e9 Msun, a large amount of gas is evacuated by photo-evaporation, results in the suppression of SF. SF in massive haloes also strongly suppressed despite the fact that these haloes hardly lose any gas---mainly caused by (i) small scale clumpy structures are smoothed by internal feedback, and (ii) dense gas in the galaxies mostly neutral, but H2 formation and cooling disturbed by mild photo-heating. Consistent with observations at z=6-7.
1209.4305
Star-formation laws in extreme starbursts
Garcia-Burillo, Usero, Alonso-Herrero
SFE of dense molecular gas (from FIR/HCN ratio) is factor 3-4 higher in extreme starbursts compared to normal galaxies. Duality on the Kennicutt-Schmidt laws. ...
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