Day 335

Monday.

1211.3415
Uncovering drivers of disk asembly: bulgeless galaxies and the stellar mass Tully-Fisher relation
Miller, Sullivan, Ellis

Assembly history of galaxies with rotating disks: examine the stellar mass TF relation over a wide range in z (Keck spectro-z sample) partitioned according to whether or not galaxies contain a prominent bulge (from HST images).  Find: bulgeless disk galaxies with z>0.8 present a significant offset from the local TF relation, whereas, at all z probed, those with significant bulges fall along the local relation.  Results support the suggestion that bulge growth may somehow expedite the maturing of disk galaxies onto the TF relation.  Discuss a variety of physical hypothesis that may explain this result in the context of kinematic observations of SF galaxies at z=0 and z>2.

1211.3417
An improved estimator for non-Gaussianity in cosmic microwave background observations
Smith, Grin, Kamionkowski

As the title says.  Standard estimators are constructed to be optimal in the Gaussian limit.  Apply a known technique to full-sky map.  As a result of the late time ISW effect, the performance of the improved estimator is degraded.  If the CMB maps are first cleaned of the ISW effect using a tracer of FG structure (eg galaxy survey or CMB WL), the new estimator does remove a majority of the excess variance, allowing a higher significance detection of fnl.

1211.3418
The mass-metallicity relation with the direct method on stacked spectra of SDSS galaxies
Andrews, Martini

The relation between galaxy stellar mass and gas-phase metallicity is a sensitive diagnostic of the main processes that drive galaxy evolution (cosmological gas inflow, metal production in stars, and gas outflow via galactic winds).  Measure metallicity of 200k SF galaxies from SDSS: stacked in bins of (1) M* and (2) both M* and SFR to get O III and O II lines for the "direct method" [?].  3 decades in stellar mass: log(M*/Msun)=7.4 to 10.5.  Mass-metallicity relation rises steeply at low mass (O/H~M*^1/2) until it turns over at M*=1e8.9Msun, and asymptotes to log(O/H)+12 = 8.8 at high mass.  Direct method has steeper slope, lower turnover mass, and a greater dependence on SFR then strong line mass-metallicity relations. SFR dependence appears monotonic with stellar mass, unlike strong line mass-metallicity relations.  [what's the significance of the mass-metallicity relation differences?!?]

1211.3420
The dark halo - spheroid conspiracy and the origin of elliptical galaxies
Remus, Burkert, Dolag, Johansson, Naab, Oser, Thomas

Dynamical modeling and SL data indicate that the total density profiles of early-type galaxies are close to isothermal (rho_tot ~ r^gamma, where gamma~-2).  Understand toe origin of this universal slope with simulated spheroids in isolated binary mergers with controlled initial conditions as well as the formation within the cosmological framework.  On average, gamma=-2.1 with a tendency towards steeper slopes for more compact, lower-mass ellipticals.  In the binary mergers, the amount of gas involved in the merger determines the steepness of the slope.  The amount of gas involved in the merger determines the steepness of the slope; agrees with cosmo sims where ellipticals with steeper slopes have a higher fraction of stars formed in-situ.  At higher z, the slopes of the ellipticals extracted from the cosmo sims are generally steeper.  Each gas-poor merger event evolves the slope towards gamma=-2; once this slope is reached, further merger events do not change the slope anymore.  Independent of their individual slopes or evolution scenarios, all ellipticals have flat intrinsic combined stellar and DM velocity dispersion profiles.  The variety of complex formation histories as present in cosmo sims, including major as well as minor merger events, is essential to generate the full range of observed density slopes seen for present day elliptical galaxies.

1211.3424
Stellar kinematics of z~2 galaxies and the inside-out growth of quiescent galaxies
van de Sande, Kriek, Franx, van Dokkum, Bezanson, ... Rix... et al

Investigate whether massive, quiescent galaxies were denser at z~2 than they are today.  Stellar kinematics from spectra in UV to NIR; dynamical mass meausrements of 5 quiescent massive (>1e11Msun) galaxies at z~2.  Find: stellar ages range from 0.5-2Gyr with no sign of on-going SF.  Measure velocity dispersions (300-450 km/s) and find that they are 1.6-2.1 times higher than those of galaxies in the SDSS at fixed mass.  Sizes are measured with GALFIT from HST image; dynamical masses correspond well to the SED-based M*, with dynamical masses that are ~15% higher.  Find M*/M_dyn may decrease slightly with time, which could reflect the increase of the DM fraction within an effective radius.  Combine different stellar kinematic studies from the literature, and examine the structural evolution from z~2 to z~0: we confirm that at fixed dynamical mass, the effective radius increases by a factor of ~2.8, and the velocity dispersion decreases by a factor of ~1.7 with time [if M_dyn = halo mass, then this means ... wait, what's happening to M*?  Is it correct to assume that M_dyn = M_halo?  Does this mean that the stars are more fluffier in the halo at later times?].  The mass density within one effective radius decreases by a factor of ~21, while within a fixed physical radius (1kpc) it decreases only mildly (~2.3).  [oh, I guess there is cosmological expansion.]  When allowed for an evolving mass limit by selecting a population of galaxies at fixed number density, a stronger size growth with time is found (~4), velocity dispersion decreases by a factor of ~1.4, and the mass density within 1kpc is consistent with no evolution.  This finding suggests that massive quiescent galaxies at z~2 grow in an inside-out matter, consistent with the expectations from minor mergers.

1211.3441
Quenching of SF in molecular outflow host NGC 1266
Alatalo, .. Graves, .. et al

AGN-driven molecular outflow in NGC 1266, potentially quenching all of its SF within the next 100 Myr.  No evidence of major interaction.  The molecular gas and the instantaneous SF tracers indicate that the current sites of SF are located in a hypercompact disk within 200 pc of the nucleus.  On the other hand, tracers of recent SF (H_beta and SPS analysis) show that the young stars are distributed throughout a larger area of the galaxy than current SF.  As the AGN at the center of the NGC 1266 continues to drive cold gas out of the galaxy, we expect SFR to decline as the SF is ultimately quenched.  Thus, NGC 1266 is in the midst of a key portion of its evolution; may want to keep a close eye on it.

1211.3663
CLASH: three strongly lensed images of a candidate z~11 galaxy
Coe, Zitrin, ... et al

As the title says.