1709.04469
Hot dust in Panchromatic SED fitting: identification of AGN and improved galaxy properties
Leja, Johnson, Conroy, van Dokkum
Forward modeling of the full galaxy SED is a powerful technique, providing self-consistent constraints on stellar ages, star formation rates, dust properties, and metallicities. However, the accuracy of these results is contingent on the accuracy of the model. One significant source of uncertainty is the contribution of obscured AGN to the SED, as they are relatively common and can produce substantial id-IR (MIR) emission. Here, include emission from dusty AGN tore in the Prospector SED-fitting framework, and fit the UV-IR broadband photometry of 129 nearby galaxies. Find that 10% of the fitted galaxies host an AGN contribution at least 10% of the total observed MIR luminosity. Demonstrate the necessity of this AGN component in the following ways. First, we compare observed spectral features to spectral features predicted from the model fit to the photometry. Find that the AGN component greatly improves predictions for observed H_alpha and H_beta luminosities, as well as MIR Akari and Spitzer/IRS spectra. Second, show that inclusion of the AGN component changes stellar ages and SFRs by up to a factor of 10, and dust attenuations by up to a factor of 2.5. Finally, show that the strength of the AGN component in the model correlates with independent AGN indicators, including X-ray fluxes, MIR color gradients, emission line ratios, and other published AGN diagnostics. This evidence strongly implies that these galaxies truly host AGN, and that the full SED modeling approach is able to detect AGN down to contrasts of L_MIR,AGN / LMIR,tot ~ 0.1. Notably, only 46% of the SED-detected AGN would be detected with a simple MIR color selection. Based on these results, conclude that SED models which do not include AGN when fitting MIR data are vulnerable to substantial bias in their derived stellar populations parameters.
1709.04484
First results on the cluster galaxy population from the Subary Hyper Suprime-Cam survey. III. Brightest cluster galaxies, stellar mass distribution, and active galaxies
Lin, et al
The unprecedented depth and area surrey by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled construction of the largest distant cluster sample out to z~1 to date. In this exploratory study of cluster galaxy evolution from z=1 to z=0.3, investigate the stellar mass assembly history of BCGs, and evolution of stellar mass and luminosity distributions ,stellar mass surface density profile, as well as the population of radio galaxies. The analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow tracing of the cluster evolution faithfully. The stellar mass is derived from a machine-learning algorithm, which is shown to be unbiased and accurate with respect to the COSMOS data. Find very mild stellar mass growth in BCGs, and no evidence for evolution in both the total stellar mass-cluster mass correlation and the shape of the stellar mass surface density profile. Also present the first measurement of the radio luminosity distribution in clusters out to z~1.
1709.05024
A search for warm/hot gas filaments between pairs of SDSS luminous red galaxies
Tanimura, et al
Search the Planck data for a thermal SZ (tSZ) signal due to gas filaments between pairs of LRG's taken from SDSS DR12. Identify ~260,000 LRG pairs in the DR12 catalog that lie within 6-10 Mpc/h of each other in tangential direction and within 6 Mpc/h in radial direction. Stack pairs by rotating and scaling the angular positions of each LRG so they lie on a common reference frame, then subtract a circularly symmetric halo from each member of the pair to search for residual signal between the pair members. Find a statistically significant (5.3 sigma) between LRG pairs in the stacked data with a magnitude Delta y=(1.31±0.25) e-8. The uncertainty is estimated from two MC nu tests which also establish the reliability of the analysis. Assuming a simple, isothermal, cylindrical filament model of electron over-density with a radial density profile proportional to r_c/r (as determined from simulations), where r is the perpendicular distance from the cylinder axis and r_c is the core radius of the density profile, constrain the product of over-density and filament temperature to be delta_c*(T_c/1e7K)*(r_c/0.5Mpc/h) = 2.7±0.5. To best knowledge, this is the first detection of filamentary gas at over-densities typical of cosmological LSS. Compare the results to the BAHAMAS suite of cosmological hydrodynamic simulations (McCarthy+2017) and find a slightly lower, but marginally consistent Comptonization excess, Delta y = (0.84±0.24)e-8.
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