92 research outputs found
Accounting for selection bias using simulations: A general method and an application to millimeter-wavelength surveys
We have developed a new Bayesian method to correct the flux densities of
astronomical sources. The hybrid method combines a simulated likelihood to
model survey selection together with an analytic source-count-based prior. The
simulated likelihood captures the effect of complicated selection methods, such
as multi-frequency filtering or imposed restrictions on recovered sample
properties (e.g., color cuts). Simulations are also able to capture
unanticipated sources of uncertainty. In this way, the method enables a broader
application of Bayesian techniques. Use of an analytic prior allows variation
of assumed source count models without re-simulating the likelihood. We present
the method along with a detailed description of an application to real survey
data from the Atacama Cosmology Telescope.Comment: 10 pages. Accepted versio
Stellar Populations of Highly Magnified Lensed Galaxies: Young Starbursts at z~2
We present a comprehensive analysis of the rest-frame UV to near-IR spectral
energy distributions and rest-frame optical spectra of four of the brightest
gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at
z=1.70, MS1512-cB58 at z=2.73, SGAS J152745.1+065219 at z=2.76 and SGAS
J122651.3+215220 at z=2.92. This includes new Spitzer imaging for RCSGA0327 as
well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and
SGAS1226. Lensing magnifications of 3-4 magnitudes allow a detailed study of
the stellar populations and physical conditions. We compare star formation
rates as measured from the SED fit, the H-alpha and [OII] emission lines, and
the UV+IR bolometric luminosity where 24 micron photometry is available. The
SFR estimate from the SED fit is consistently higher than the other indicators,
which suggests that the Calzetti dust extinction law used in the SED fitting is
too flat for young star-forming galaxies at z~2. Our analysis finds similar
stellar population parameters for all four lensed galaxies: stellar masses
3-7*10^9 M_sun, young ages ~ 100 Myr, little dust content E(B-V)=0.10-0.25, and
star formation rates around 20-100 M_sun/yr. Compared to typical values for the
galaxy population at z~2, this suggests we are looking at newly formed,
starbursting systems that have only recently started the build-up of stellar
mass. These results constitute the first detailed, uniform analysis of a sample
of the growing number of strongly lensed galaxies known at z~2.Comment: 13 pages, 8 figures, Accepted to Ap
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Weak-lensing Mass Calibration of ACTPol SunyaevâZelâdovich Clusters with the Hyper Suprime-Cam Survey
We present weak-lensing measurements using the first-year data from the Hyper Suprime-Cam Strategic Survey Program on the Subaru telescope for eight galaxy clusters selected through their thermal SunyaevâZel'dovich (SZ) signal measured at 148 GHz with the Atacama Cosmology Telescope Polarimeter experiment. The overlap between the two surveys in this work is 33.8 square degrees, before masking bright stars. The signal-to-noise ratio of individual cluster lensing measurements ranges from 2.2 to 8.7, with a total of 11.1 for the stacked cluster weak-lensing signal. We fit for an average weak-lensing mass distribution using three different profiles, a NavarroâFrenkâWhite profile, a dark-matter-only emulated profile, and a full cosmological hydrodynamic emulated profile. We interpret the differences among the masses inferred by these models as a systematic error of 10%, which is currently smaller than the statistical error. We obtain the ratio of the SZ-estimated mass to the lensing-estimated mass (the so-called hydrostatic mass bias 1âb) of , which is comparable to previous SZ-selected clusters from the Atacama Cosmology Telescope and from the Planck Satellite. We conclude with a discussion of the implications for cosmological parameters inferred from cluster abundances compared to cosmic microwave background primary anisotropy measurements.U.S. National Science Foundation [AST-1440226, AST-0965625, AST-0408698, PHY-1214379, PHY-0855887]; Princeton University; University of Pennsylvania; Canada Foundation for Innovation (CFI) award; Comision Nacional de Investigacion Cientifica y Tecnologica de Chile (CONICYT); CFI under Compute Canada; Government of Ontario; Ontario Research Fund Research Excellence; University of Toronto; NASA [NNX13AE56G, NNX14AB58G]; FIRST program from Japanese Cabinet Office; Ministry of Education, Culture, Sports, Science and Technology (MEXT); Japan Society for the Promotion of Science (JSPS); Japan Science and Technology Agency (JST); Toray Science Foundation; NAOJ; Kavli IPMU; KEK; ASIAA; National Aeronautics and Space Administration [NNX08AR22G]; National Science Foundation [AST-1238877]; Jet Propulsion Laboratory, California Institute of Technology; National Aeronautics and Space Administration; Japan Society for the Promotion of Science (JSPS) KAKENHI [JP17H06600, JP18H04350]; Simons Foundation; JSPS KAKENHI [JP16H01089]; STFC Ernest Rutherford Fellowship [ST/M004856/2]; National Research Foundation of South Africa [93565]; CONICYT FONDECYT grant [3170846]; JSPS KAKENHI grant [JP17K14273, JP15H03654, JP15H05893, JP15K21733, JP15H05892]; Japan Science and Technology Agency (JST) CREST [JPMJCR1414]; Ministry of Science and Technology of Taiwan [MOST 103-2628-M-001-003-MY3]; Academia Sinica Investigator Award; Vincent and Beatrice Tremaine Fellowship; [Anillo ACT-1417]; [QUIMAL-160009]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
A measurement of the millimetre emission and the SunyaevâZel'dovich effect associated with low-frequency radio sources
We present a statistical analysis of the millimetre-wavelength properties of 1.4âGHz-selected sources and a detection of the SunyaevâZel'dovich (SZ) effect associated with the haloes that host them. We stack data at 148, 218 and 277âGHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4âGHz. The thermal SZ effect associated with the haloes that host the AGN is detected at the 5Ï level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass haloes (average M_(200) â 10^(13) Mâ h^(â1)_(70) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous haloes. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyse the contribution of radio sources to the angular power spectrum of the cosmic microwave background
CARMA Measurements of the Sunyaev-Zel'dovich Effect in RXJ1347.5-1145
We demonstrate the Sunyaev-Zel'dovich (SZ) effect imaging capabilities of the
Combined Array for Research in Millimeter-wave Astronomy (CARMA) by presenting
an SZ map of the galaxy cluster RXJ1347.5-1145. By combining data from multiple
CARMA bands and configurations, we are able to capture the structure of this
cluster over a wide range of angular scales, from its bulk properties to its
core morphology. We find that roughly 9% of this cluster's thermal energy is
associated with sub-arcminute-scale structure imparted by a merger,
illustrating the value of high-resolution SZ measurements for pursuing cluster
astrophysics and for understanding the scatter in SZ scaling relations. We also
find that the cluster's SZ signal is lower in amplitude than suggested by a
spherically-symmetric model derived from X-ray data, consistent with
compression along the line of sight relative to the plane of the sky. Finally,
we discuss the impact of upgrades currently in progress that will further
enhance CARMA's power as an SZ imaging instrument.Comment: 8 pages, 6 figure
The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey
We present a catalog of 191 extragalactic sources detected by the Atacama
Cosmology Telescope (ACT) at 148 GHz and/or 218 GHz in the 2008 Southern
survey. Flux densities span 14-1700 mJy, and we use source spectral indices
derived using ACT-only data to divide our sources into two sub-populations: 167
radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty
star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the
AGN and 19 of the DSFGs) with those in currently available catalogs. When
combined with flux densities from the Australian Telescope 20 GHz survey and
follow-up observations with the Australia Telescope Compact Array, the
synchrotron-dominated population is seen to exhibit a steepening of the slope
of the spectral energy distribution from 20 to 148 GHz, with the trend
continuing to 218 GHz. The ACT dust-dominated source population has a median
spectral index of 3.7+0.62-0.86, and includes both local galaxies and sources
with redshifts as great as 5.6. Dusty sources with no counterpart in existing
catalogs likely belong to a recently discovered subpopulation of DSFGs lensed
by foreground galaxies or galaxy groups.Comment: 13 pages, 8 figures, 4 table
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