Tuesday.
1209.3305
Solving the cooling flow problem through mechanical AGN feedback
Gaspari, Brighenti, Ruszkowski
X-ray observation indicate AGN heating as the balancing counterpart of cooling. Argue: mechanical feedback (massive subrelativistic outflows) is key to solving the cooling flow problem (dramatically quenching the cooling rates for several Gyr without destroying the cool-core structure). Used 3d hydrocode FLASH: show AGN outflow can further reproduced buoyant bubbles, weak shocks, metal dredge-up and turbulence (fundamental observed features). Turbulence essential to drive NL thermal instabilities, causing the formation of extended cold gas, a residual of the quenched cooling flow and, later, fuel for the feedback engine. Compared to clusters, groups and galaxies require a gentler mechanical feedback, in order to avoid catastrophic overheating. Highlight the essential characteristics for a realistic AGN feedback, with emphasis on observational consistency.
1209.3306
A re-examination of galactic conformity and a comparison with semi-analytic models of galaxy formation
Kauffmann, Li, Zhang, Weinmann
Observed correlation between SF in central galaxies and in their neighbors ("galactic conformity") needs physical explanation. From SDSS DR7, local galaxies (z<0.03): conformity extends over a central galaxy stellar mass range spanning 2 orders of magnitude. In central galaxies with masses less than 1e10 Msun, conformity extends out to scales >4Mpc, well beyond the virial radii of their DM haloes. For low mass central galaxies, large-scale conformity with neighbours is only seen when the centrals have low SFR or gas content. At high stellar masses, conformity with neighbours applies in the gas-rich regime, clearly confined to scales comparable to virial radius of DM halo of the central galaxy. Mock catalogue from Guo+(2011) does not show conformity. Conformity between low-mass, gas-poor central galaxies and their distant neighbours cannot be explained within the framework of HOD models. Likely a signature of pre-heating of IGM gas at an earlier epoch [really?]. Smaller scale conformity between high-mass, gas-rich central galaxies and close neighbours may be a signature of ongoing gas accretion onto central galaxies in a minority of massive DM haloes.
1209.3039
Rhapsody: I. structural properties and formation history from a statistical sample of re-simulated cluster-size haloes
Wu, Hahn, Wechsler, Mao, Behroozi
Using 96 "zoom-in" simulations of DM haloes of 1e14.8 Msun/h selected from 1Gpc^3 volume, study properties of main haloes and how they are affected by formation history (back to z=12) over 5 decades in mass. Deviation from NFW/Einasto depend on formation time. Late-forming haloes tend to have considerable deviations from both models, partly due to massive sub haloes, while early-forming haloes deviate less, but still significantly, from NFW model, and are better described by Einasto. Find: halo shapes depend only moderately on formation time. Departure from spherical symmetry impacts the density profiles through the anisotropic distribution of massive subhaloes [the other way around?]. Further evidence of impact of subhaloes provided by analyzing the phase-space structure. A detailed analysis of the properties of the subhalo population in Rhapsody presented in another paper.
1209.3320
Project Lyman: quantifying 11 Gyrs of metagalactic ionizing background evolution
McCandliss et al
Timing and duration of reioinization epoch: the photon escape count from SF galaxies is used to "fine-tune" the timing and duration between 13.4 and 12.7 Gyrs ago (12<z<6). Direct observation of Lyman continuum (LyC) increasingly improbable at z>3 due to steady increase of intervening Lyman limit systems towards high z. Thus UV and U-band optical bandpasses provide the only hope for direct observations of the types of environment that favor LyC escape. Observation will provide crucial LyC escape fraction info. [white paper for NASA]
1209.3325
A fast flare and direct redshift constraint in far-UV spectra of the blazar S50716+714
Danforth et al
Constrain z from the flare (a first), consistent with host galaxy redshift.
1209.3339
Annual modulation of dark matter: a review
Freese, Lisanti, Savage
For standard assumptions, the count rate has a cosine dependence over time (maximum in June). Presence of substructure in galactic halo, interactions between dark and baryonic matter, can also be probed.
1209.3457
Seeing the first supernovae at the edge of the universe with JWST
Whalen, Fryer, Holz, ... et al
Masses of PopIII stars can be estimated from their SNe explosions. JWST and WFIRST will detect these explosions out to z~30 and 20, respectively.
1209.3473
The accuracy of the UV continuum as an indicator of the star formation rate in galaxies
Wilkins et al
The rest-frame UV luminosity often used as indicator of instantaneous SFR in a galaxy, but the precise value of calibration relating the UV luminosity to SFR is sensitive to various physical properties (e.g., recent SF and metal enrichment histories, choice of IMF). So a single calibration is not appropriate, based on the distribution of these properties. And that's what they find.
1209.3498
H{\alpha} and UV luminosities and star formation rates in a large sample of luminous compact galaxies
Parnovsky, Izotova, Izotov
Results of SFR study from GALEX observations in 800 LCGs. Global galaxy characteristics (Z, L, M*) are intermediate between nearby blue compact dwarf and high-z (z>2-3) Lyman break galaxies. SFRs corrected for interstellar extinction derived from SDSS spectra. SFR derived from FUV and NUV vary a wide range (0.18 to 113 Msun/yr), with median of 3.8 and 5.2 Msun/yr, respectively. Consider evolution of L with SB age, and introduce new characteristics (the luminosity of Ha, FUV and NUV) at zero SB age.
1209.3635
On the origin of elemental abundances in the terrestrial planets
Elser, Meyer, Moore
Combine circumstellar disk models, chemical equilibrium calculations, dynamical simulations of planet formation to study bulk composition of rocky planets. Condensation sequence modeled to estimate the initial abundance of solids in the disk; planetesimal growth also modeled. Calculate elemental abundances in the resulting planets. No model could reproduce the abundance properties of all planets. Choice of initial planetsimal disk mass and disk model has significant effect on composition gradients. Higher pressure and temperature in disk result in larger variations in the bulk chemical compositions. Massive planets and planets with small semi-major axis are more sensitive to these variations than smaller planets at larger radial distance. Only these large variations in the simulated abundances can potentially explain the diverse bulk composition of the SS planets. Mercury's bulk composition can not be reproduced in these models.
1209.3665
Gas fraction and star formation efficiency at z<1.0
Combes et al
Observation of 39 galaxies at 0.6<z<1.0 added to the full CO line survey in 0.2<z<1. Study the decline of SFR in this epoch. Find gas fraction in sample increases strongly with redshift, and is the most determining factor in the cosmic SF evolution. The SFE evolution is shallower; conlucde that it plays a less significant role in setting the cosmic SFE.
1209.3305
Solving the cooling flow problem through mechanical AGN feedback
Gaspari, Brighenti, Ruszkowski
X-ray observation indicate AGN heating as the balancing counterpart of cooling. Argue: mechanical feedback (massive subrelativistic outflows) is key to solving the cooling flow problem (dramatically quenching the cooling rates for several Gyr without destroying the cool-core structure). Used 3d hydrocode FLASH: show AGN outflow can further reproduced buoyant bubbles, weak shocks, metal dredge-up and turbulence (fundamental observed features). Turbulence essential to drive NL thermal instabilities, causing the formation of extended cold gas, a residual of the quenched cooling flow and, later, fuel for the feedback engine. Compared to clusters, groups and galaxies require a gentler mechanical feedback, in order to avoid catastrophic overheating. Highlight the essential characteristics for a realistic AGN feedback, with emphasis on observational consistency.
1209.3306
A re-examination of galactic conformity and a comparison with semi-analytic models of galaxy formation
Kauffmann, Li, Zhang, Weinmann
Observed correlation between SF in central galaxies and in their neighbors ("galactic conformity") needs physical explanation. From SDSS DR7, local galaxies (z<0.03): conformity extends over a central galaxy stellar mass range spanning 2 orders of magnitude. In central galaxies with masses less than 1e10 Msun, conformity extends out to scales >4Mpc, well beyond the virial radii of their DM haloes. For low mass central galaxies, large-scale conformity with neighbours is only seen when the centrals have low SFR or gas content. At high stellar masses, conformity with neighbours applies in the gas-rich regime, clearly confined to scales comparable to virial radius of DM halo of the central galaxy. Mock catalogue from Guo+(2011) does not show conformity. Conformity between low-mass, gas-poor central galaxies and their distant neighbours cannot be explained within the framework of HOD models. Likely a signature of pre-heating of IGM gas at an earlier epoch [really?]. Smaller scale conformity between high-mass, gas-rich central galaxies and close neighbours may be a signature of ongoing gas accretion onto central galaxies in a minority of massive DM haloes.
1209.3039
Rhapsody: I. structural properties and formation history from a statistical sample of re-simulated cluster-size haloes
Wu, Hahn, Wechsler, Mao, Behroozi
Using 96 "zoom-in" simulations of DM haloes of 1e14.8 Msun/h selected from 1Gpc^3 volume, study properties of main haloes and how they are affected by formation history (back to z=12) over 5 decades in mass. Deviation from NFW/Einasto depend on formation time. Late-forming haloes tend to have considerable deviations from both models, partly due to massive sub haloes, while early-forming haloes deviate less, but still significantly, from NFW model, and are better described by Einasto. Find: halo shapes depend only moderately on formation time. Departure from spherical symmetry impacts the density profiles through the anisotropic distribution of massive subhaloes [the other way around?]. Further evidence of impact of subhaloes provided by analyzing the phase-space structure. A detailed analysis of the properties of the subhalo population in Rhapsody presented in another paper.
1209.3320
Project Lyman: quantifying 11 Gyrs of metagalactic ionizing background evolution
McCandliss et al
Timing and duration of reioinization epoch: the photon escape count from SF galaxies is used to "fine-tune" the timing and duration between 13.4 and 12.7 Gyrs ago (12<z<6). Direct observation of Lyman continuum (LyC) increasingly improbable at z>3 due to steady increase of intervening Lyman limit systems towards high z. Thus UV and U-band optical bandpasses provide the only hope for direct observations of the types of environment that favor LyC escape. Observation will provide crucial LyC escape fraction info. [white paper for NASA]
1209.3325
A fast flare and direct redshift constraint in far-UV spectra of the blazar S50716+714
Danforth et al
Constrain z from the flare (a first), consistent with host galaxy redshift.
1209.3339
Annual modulation of dark matter: a review
Freese, Lisanti, Savage
For standard assumptions, the count rate has a cosine dependence over time (maximum in June). Presence of substructure in galactic halo, interactions between dark and baryonic matter, can also be probed.
1209.3457
Seeing the first supernovae at the edge of the universe with JWST
Whalen, Fryer, Holz, ... et al
Masses of PopIII stars can be estimated from their SNe explosions. JWST and WFIRST will detect these explosions out to z~30 and 20, respectively.
1209.3473
The accuracy of the UV continuum as an indicator of the star formation rate in galaxies
Wilkins et al
The rest-frame UV luminosity often used as indicator of instantaneous SFR in a galaxy, but the precise value of calibration relating the UV luminosity to SFR is sensitive to various physical properties (e.g., recent SF and metal enrichment histories, choice of IMF). So a single calibration is not appropriate, based on the distribution of these properties. And that's what they find.
1209.3498
H{\alpha} and UV luminosities and star formation rates in a large sample of luminous compact galaxies
Parnovsky, Izotova, Izotov
Results of SFR study from GALEX observations in 800 LCGs. Global galaxy characteristics (Z, L, M*) are intermediate between nearby blue compact dwarf and high-z (z>2-3) Lyman break galaxies. SFRs corrected for interstellar extinction derived from SDSS spectra. SFR derived from FUV and NUV vary a wide range (0.18 to 113 Msun/yr), with median of 3.8 and 5.2 Msun/yr, respectively. Consider evolution of L with SB age, and introduce new characteristics (the luminosity of Ha, FUV and NUV) at zero SB age.
1209.3635
On the origin of elemental abundances in the terrestrial planets
Elser, Meyer, Moore
Combine circumstellar disk models, chemical equilibrium calculations, dynamical simulations of planet formation to study bulk composition of rocky planets. Condensation sequence modeled to estimate the initial abundance of solids in the disk; planetesimal growth also modeled. Calculate elemental abundances in the resulting planets. No model could reproduce the abundance properties of all planets. Choice of initial planetsimal disk mass and disk model has significant effect on composition gradients. Higher pressure and temperature in disk result in larger variations in the bulk chemical compositions. Massive planets and planets with small semi-major axis are more sensitive to these variations than smaller planets at larger radial distance. Only these large variations in the simulated abundances can potentially explain the diverse bulk composition of the SS planets. Mercury's bulk composition can not be reproduced in these models.
1209.3665
Gas fraction and star formation efficiency at z<1.0
Combes et al
Observation of 39 galaxies at 0.6<z<1.0 added to the full CO line survey in 0.2<z<1. Study the decline of SFR in this epoch. Find gas fraction in sample increases strongly with redshift, and is the most determining factor in the cosmic SF evolution. The SFE evolution is shallower; conlucde that it plays a less significant role in setting the cosmic SFE.
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