Day 170

Tuesday.  First Aikido class in Bonn last night.  Came home exhausted, took a bath, was great.  Tonight is Rock Climbing.


1112.3959
The ongoing assembly of a central cluster galaxy: Phase-space substructures in the halo of M87
Romanowsky, Strader, Brodie, Mihos, Spitler, Forbes, Foster, Arnold


Combined observational and theoretical study of phase-space halo substructure in an early-type galaxy: M87, the central galaxy in the Virgo cluster.  Use photometry and spectroscopy of 488 globular clusters (GCs), find signatures of two substructures in position-velocity phase-space.  One is a small, cold stream associated with a known stellar filament in the outer halo; the other is a large shell-like pattern in the inner halo that implies a massive, hitherto unrecognized accretion event.  Study metallicity, etc.  Cold outer stream is consistent with a dwarf galaxy accretion event, the inner shell has tension between a low progenitor mass implied by the cold velocity dispersion, and a high mass from the number of GCs, which might be resolved by a ~0.5L* E/S0 progenitor.  Numerical sims of accretion of smaller galaxies in an M87-like gravitational potential, produce analogous features to the observed substructures, which should have observable lifetimes of ~1Gyr.  Shell and stream GCs together support a scenario where the extended stellar envelope of M87 has been build up by a steady rain of material that continues until the present day.  This phase-space method demonstrates unique potential for detailed tests of galaxy formation beyond the Local Group.


1112.3963
The luminous infrared host galaxy of short-duration GRB 100206A
Perley, Modjaz, Morgan, Cenko, Bloom, Butler, Filippenko, MIller


The known host galaxies of short-hard gamma-ray bursts (GRBs) to date are characterized by low to moderate star-formation rates and a broad range of stellar masses.  This GRB is associated with a disk galaxy at z=0.4068 with SFR of 30 Msun/yr (high SFR!).  Galaxy is very red, heavily obscured, and has the highest metallicity of any GRB host to date (LIRG).  Old star population also present in this galaxy.  Most likely this GRB had a older progenitor (that implied by the recent SF).


1112.3970
Host Galaxy morphology and the AGN unified model
Trump


Unobscured and rapidly accreting borad-line AGNs are more likely to be in spheroid-dominated hosts than weak or obscured AGNs and obscured AGNs are more likely to have disturbed host galaxies.  Obscured AGNs seem to be merger-driven, while weak AGNs are fed by stochastic processes in disks, and rapidly-accreting broad-line AGNs require massive bulges.  


1112.3990
The relation between galaxy morphology and environment in the local universe: An RC3-SDSS picture
Wilman, Erwin


Fraction of galaxies which are elliptical is a strong function of stellar mass; it is also a strong function of halo mass, but only for central galaxies.  Satellite S0 galaxies are only found in massive (>1e13 Msun) haloes.  Suggests two channels for forming S0 galaxies: one for central galaxies, and one for disk galaxies accreting onto a massive halo.  Bars are not strongly influenced by galaxy environment.  Radio sources in high-mass central galaxies are common, similarly so for ellipticals and S0s, with frequency increasing with halo mass.  Emission-line AGNs (mostly LINERs) are common in S0s but show no strong trends with environment.


1112.3997
The first systematic survey for Lyman Alpha emitters at z=7.3 with red-sensitive Subaru-Suprime cam
Shibuya, Kashikawa, Ota, Iya, Ouchi, Furusawa, Shimasaku, Hattori


Search for LAE at z~7.2 yielded: 4 candidates (from narrow-band photometry), 3 deep spectroscopic followups.  One was a probable LAE at z=7.2 with asymmetric emission line with SFR of 11 Msun/yr.  Another is variable and is thus probably a QSO at either z=7.2 (if LyA) or z=1.7 (if OII line).  The third object is likely a galaxy with temporal luminosity enhancement associated with SNe explosion.  Infers a decrease in the number density of LAEs toward higher redshift, consistent with interpretation in previous studies that the neutral hydrogen fraction is rapidly increasing from z=5.7 to 7.3.


1112.4058
Do disk galaxies with abnormally low mass-to-light ratios exist?
Saburova, Bizyaev, Zasov


The answer is, not really--most of the candidates for low M/L ratio (implied by BVR colors) were actually errors in photometry of rotational velocity.  But a handful (3) of the galaxies seem to have low M/L ratio.  Implies that IMF is universal, and that only a small fraction of galaxies may have non-typical low-mass star depleted initial mass function.  Might want to study these more.


1112.4070
Simulating protostellar evolution and radiative feedback in the cluster environment
Klassen, Pudritz, Peters


Radiative feedback is among the most important consequences of clustered star formation inside molecular clouds.  At onset of SF, radiation from massive stars heats the surrounding gas, which suppresses the formation of many low-mass stars.  Must use prestellar model to simulate pre-main-sequence stars.  Compare two existing prestellar models under identical initial conditions to gauge whether the choice of model has effect on the final population of stars.  First model: treats stellar radii and luminosities with ZAMS model, while separately estimating the accretion luminosity by interpolating to published prestellar tacks [?].  The second, more accurate prestellar model self-consistently evolves the radius and luminosity of each star under highly variable accretion conditions.  Each coupled to radiative feedback code that also treats inoization.  Impact of the self-consistent model is less ionizing radiation and less heating during the early stages of star formation.  Peak stellar mass reduced by 8% in the evolutionary model, relative to the track-fit model.  The difference in mass between the two largest stars in each case is reduced from 14 Msun to 7.5 Msun.  The HII regions produced by these massive stars seen to flicker on timescales down to the timestep (<560 yrs), confirming previous cluster simulations using ZAMS-based estimates for prestellar inoizing flux.  [what was the result of the comparison?  is one better than the other???]


1112.4157
Variable accretion rates and fluffy first stars
Smith, Hosokawa, Omukai, Glover, Klessen


Combine Hydrodynamical sims of Pop III star cluster formation with stellar evolution models, and calculate the evolution of protostars experiencing variable mass accretion rates due to interactions within a massive disk.  Find: primordial protostars are extended "fluffy" objects for the bulk of their pre-MS lifetimes.  Accretion luminosity feedback is high but has minimal effect on the star cluster.  Extended radii of the protostars, combined with the observation of close encounters in the simulations, suggests that mergers will occur in such systems.  Mass transfer between close protostellar binaries with extended radii could lead to massive tight binaries, which are possible progenitor of gamma ray bursts.