Day 650

Thursday.

1405.1043
Hot gas in massive haloes drives both mass quenching and environmental quenching
Gabor, Davé

Galaxies with high M* or in dense environments have low sSFRs (they are quenched).  Based on cosmological hydrodynamic simulations that include a prescription where quenching occurs in regions dominated by hot (>1e5K) gas, argue that this hot gas quenching in haloes >1e12 Msun drives both mass quenching (i.e., central quenching) and environment quenching (i.e. satellite quenching).  These simulations reproduce a broad range of locally observed trends among quenching, halo mass, stellar mass, environment, and distance to halo center.  Show that mass quenching is independent of environment because 1e12-13 Msun "quenching haloes" -- those where most mass quenching occurs -- inhabit a large range of environments.  On the other hand, environment quenching is independent of stellar mass because galaxies of all stellar masses may live in dense environments as satellite of groups and clusters.  Furthermore, satellite galaxies show signs of mass quenching independent of halo mass because massive satellites at z=0 have typically been mass quenched as centrals in their own hot halos at higher z --- a kind of pre-processing.  As in observations, the fraction of quenched satellites increases with halo mass and decreases with distance to the center of the group or cluster.  Investigate quenched centrals in low-mass haloes (<1e12 Msun), and show that most of these are ejected former satellites of groups or clusters, while about 20% were never satellites but are enveloped in hot gas that extends up to 3 Rvir from the centers of clusters.  The agreement of the model with key observational trends suggests that hot gas in massive haloes plays a leading role in quenching low-z galaxies.

1405.1047
Extremely red quasars from SDSS, BOSS and WISE: Classification of optical spectra
Ross, … Zakamska, Richards, Strauss, … et al

Quasars with extremely red colors are an interesting population that can test ideas about quasar evolution as well as orientation and geometric effects in the so-called AGN unified model.  To identify such a population, search the quasar analogs of SDSS, BOSS and WISE for quasars with extremely high IR-to-optical ratios.  Identify 65 objects with r(AB)-W4(Vega)>14 mag (i.e., F_nu(22um)/F_nu®>~1000).  This sample spans a redshift range of 0.28<z<4.36 with a median of z~1.5 and includes three z>2.6 objects that are detected in the W4-band but not W1 or W2 (i.e., "W1W2-dorpouts").  The SDSS/BOSS spectra show that the majority of the objects are reddened Type1 quasars, Type 2 quasars (both at low and high z) or objects with deep low-ionization broad absorption lines (BALs) that suppress the observed r-band flux.  In addition, identify a class of Type 1 permitted broad-emission line objects at z~2-3 which are characterized by emission line rest-frame EWs of >~150A not characteristic of typical quasars.  For example, 55% (45%) of the non-BAL type 1s with measurable CIV in our sample have REW(CIV)>100(150)A, compared to only 5.8% (1.3%) for non-BAL quasars generally in BOSS.  These objects often also have unusual line properties including unusually high NV/Ly-a ratios.  These large REWs might be caused by suppressed continuum emission analogous to Type 2 quasars; however, there is no obvious mechanism in the Unified Model to suppress the continuum without also obscuring the broad emission lines.

1405.1048
Exploring the z=3-4 massive galaxy population with ZFOURGE: the prevalence of dusty and quiescent galaxies
Spitler et al

z>3 galaxy population selection relies largely on the "dropout" technique, typically consisting of UV-bright galaxies with blue colors and prominent Lyman breaks.  As it is currently unknown if these galaxies are representative of the massive galaxy population, use ZFOURGE survey to create a stellar mass-limited sample at z=3-4.  Uniquely, ZFOURGE uses deep NIR medium-bandwidth filters to derive accurate photo-zs and stellar population properties.  The mass-complete sample consists of 57 galaxies with log M>10.6, reaching below M* at z=3-4.  On average, the massive z=3-4 galaxies are extremely faint in the observed optical with median R_tot^AB=27.5 (rest frame M1700=-18.1).  They lie far below the UV luminosity-stellar mass relation for Lyman break galaxies and are about ~100x fainter at the same mass.  The massive galaxies are red (R-K_s_AB=3.9pm0.2, rest frame UV-slope beta = -0.2pm0.3) likely from dust or old stellar ages.  Classify the galaxy SEDs by their rest frame U-V and V-J colors and find a diverse population: 46pm20% of the massive galaxies are quiescent, 54pm25% are dusty SF galaxies, and only 14pm14% resemble luminous blue star forming Lyman break galaxies.  This study clearly demonstrates an inherent diversity among massive galaxies at higher z than previously known.  Furthermore, uncover a reservoir of dusty SF galaxies with 4x lower sSFRs compared to submillimeter-selected starbursts at z>3.  With 5x higher numbers, the dusty galaxies may represent a more typical mode of SF compared to submillimeter-bright starbursts.

1405.1072
IGM constraints form the SDSS-III/BOSS DR9 Ly-alpha forest flux probability distribution function
Lee, Hennawi, Spergel, Weinberg, Hogg, Viel, Bolton, Bailey, … Schlegel, … Suzuki, et al

The Lya forest flux PDF is an established probe of the IGM astrophysics, especially the temperature-density relationship of the IGM.  Measure the flux PDF from 3393 BOSS quasars from DR9, and compare with mock spectra that include careful modeling of the noise, continuum, and astrophysical uncertainties.  The BOSS flux PDFs, measured at <z>=[2.3, 2.6, 3.0] are compared with PDFs created from mock spectra drawn from a suite of hydro sims that sample the IGM temperature-density relationship, gamma, and temperature at mean-density, T_0, where T(\Delta)=T_0\Delta^{gamma-1}.  Find that a significant population of partial Lyman-limit systems which a column-density distribution slope of beta_pLLS~-2 are required to explain the data at the low-flux end of flux PDF, while uncertainties in the mean lay forest transmission affect the high-flux end.  After modeling the LLSs and marginalizing over mean-transmission uncertainties, find that gamma=1.6 best describes the data over the entire redshift range, although constraints on T_0 are affected by systematic uncertainties.  Isothermal or inverted temperature-density relationships (gamma<1) are disfavored at a significance of >4 sigma.

1405.1077
The impact of galaxy cluster environment on the deflation properties of extragalactic gravitational lenses
Poplavsky

The influence of a galaxy cluster halo on the deflection properties of its galaxies investigated.  Triaixal cluster halo models developed based on Einasto and NFW density profiles.  Applying MC technique, external shear and convergence are modeled for random positions of a test galaxy within the cluster.  In the simulations the following parameters of the cluster and galaxies are varied: density profile, its slope, mass, characteristic and outer radii.  Also, galaxies in the close vicinity are treated separately, whereas distant objects are contributed to the smooth mass distribution.  As a result of the multiple simulations robust estimations of external shear and convergence as well as their constraints relative to variable cluster parameters and observer location effects are derived.  It is demonstrated that the external deflection by the cluster has strongly depends on the applied density profile.

1405.1216
Dust production in Supernovae
Cherchneff

SNe have long been proposed to be efficient dust producers in galaxies.  Observations in the MIR indicate that dust forms a few hundred dates after the stellar explosion.  Yet, the chemical type and the amount of dust produced by SNe are not well quantified.  In this review, summarize the current knowledge of dust formation derived from observations of SNe, present the various theoretical models on dust synthesis and their predictions, and discuss these results in the context of the most recent observations of dust in SN remnants.

1405.1390
A note of clarification: BICEP2 and Planck are not in tension
Audren, Figueroa, Tram

The apparent discrepancy between the value of the tensor-to-scalar ratio reported by the BICEP2 collaboration, r=0.20 at 68% CL, and the Palnck upper limit, r<0.11 at 95% CL, has attracted a great deal of attention.  In this short note, show that this discrepancy is mainly due to an 'apples to oranges' comparison.  The result reported by BICEP2 was measured at a pivot scale relation n_t=-r/8.  One should obviously compare the BICEP2 and Planck results under the same circumstances.  By imposing n_t=0, the Planck constraint at k*=0.05 Mpc^-1 becomes r<0.135 at 95CL, which can be compared directly with the BICEP2 result.  Once a plausible dust contribution to the BICEP2 signal is taken into account (DDM2 model), r is reduced to r=0.16pm0.05 and the discrepancy becomes of order 1.3sigma only.