arXiv subjects

Yen-Ting Lin

Publications and source records attributed to Yen-Ting Lin.

At least 127 records · Page 7Linked to original sources

arXiv2011

The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III

The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with new instrumentation and new surveys focused on Galactic structure and chemical evolution, measurements of the baryon oscillation feature in the clustering of galaxies and the quasar Ly alpha forest, and a radial velocity search for planets around ~8000 stars. This paper describes the first data release of SDSS-III (and the eighth counting from the beginning of the SDSS). The release includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap, bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a third of the Celestial Sphere. All the imaging data have been reprocessed with an improved sky-subtraction algorithm and a final, self-consistent photometric recalibration and flat-field determination. This release also includes all data from the second phase of the Sloan Extension for Galactic Understanding and Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars at both high and low Galactic latitudes. All the more than half a million stellar spectra obtained with the SDSS spectrograph have been reprocessed through an improved stellar parameters pipeline, which has better determination of metallicity for high metallicity stars.

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arXiv2011

Correlations in the (Sub)millimeter background from ACTxBLAST

We present measurements of the auto- and cross-frequency correlation power spectra of the cosmic (sub)millimeter background at: 250, 350, and 500 um (1200, 860, and 600 GHz) from observations made with the Balloon-borne Large Aperture Submillimeter Telescope, BLAST; and at 1380 and 2030 um (218 and 148 GHz) from observations made with the Atacama Cosmology Telescope, ACT. The overlapping observations cover 8.6 deg^2 in an area relatively free of Galactic dust near the south ecliptic pole (SEP). The ACT bands are sensitive to radiation from the CMB, the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio and dusty star-forming galaxies (DSFGs), while the dominant contribution to the BLAST bands is from DSFGs. We confirm and extend the BLAST analysis of clustering with an independent pipeline, and also detect correlations between the ACT and BLAST maps at over 25sigma significance, which we interpret as a detection of the DSFGs in the ACT maps. In addition to a Poisson component in the cross-frequency power spectra, we detect a clustered signal at >4sigma, and using a model for the DSFG evolution and number counts, we successfully fit all our spectra with a linear clustering model and a bias that depends only on redshift and not on scale. Finally, the data are compared to, and generally agree with, phenomenological models for the DSFG population. This study represents a first of its kind, and demonstrates the constraining power of the cross-frequency correlation technique to constrain models for the DSFGs. Similar analyses with more data will impose tight constraints on future models.

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arXiv2010

The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect

We present constraints on cosmological parameters based on a sample of Sunyaev-Zel'dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives sigma_8 = 0.851 +/- 0.115 and w = -1.14 +/- 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find sigma_8 = 0.821 +/- 0.044 and w = -1.05 +/- 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give sigma_8 = 0.802 +/- 0.038 and w = -0.98 +/- 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.

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arXiv2010

The Atacama Cosmology Telescope: Physical Properties and Purity of a Galaxy Cluster Sample Selected via the Sunyaev-Zel'dovich Effect

We present optical and X-ray properties for the first confirmed galaxy cluster sample selected by the Sunyaev-Zel'dovich Effect from 148 GHz maps over 455 square degrees of sky made with the Atacama Cosmology Telescope. These maps, coupled with multi-band imaging on 4-meter-class optical telescopes, have yielded a sample of 23 galaxy clusters with redshifts between 0.118 and 1.066. Of these 23 clusters, 10 are newly discovered. The selection of this sample is approximately mass limited and essentially independent of redshift. We provide optical positions, images, redshifts and X-ray fluxes and luminosities for the full sample, and X-ray temperatures of an important subset. The mass limit of the full sample is around 8e14 Msun, with a number distribution that peaks around a redshift of 0.4. For the 10 highest significance SZE-selected cluster candidates, all of which are optically confirmed, the mass threshold is 1e15 Msun and the redshift range is 0.167 to 1.066. Archival observations from Chandra, XMM-Newton, and ROSAT provide X-ray luminosities and temperatures that are broadly consistent with this mass threshold. Our optical follow-up procedure also allowed us to assess the purity of the ACT cluster sample. Eighty (one hundred) percent of the 148 GHz candidates with signal-to-noise ratios greater than 5.1 (5.7) are confirmed as massive clusters. The reported sample represents one of the largest SZE-selected sample of massive clusters over all redshifts within a cosmologically-significant survey volume, which will enable cosmological studies as well as future studies on the evolution, morphology, and stellar populations in the most massive clusters in the Universe.

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arXiv2010

On the Populations of Radio Galaxies with Extended Morphology at z<0.3

Extended extragalactic radio sources have traditionally been classified into FR I and II types, based on the ratio r of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source. Here we examine the distribution of various physical properties as a function of r of 1040 luminous radio galaxies (RGs) at z<0.3 from the SDSS, NVSS, and FIRST. About 2/3 of the RGs are lobe-dominated (LD), and 1/3 have prominent jets. If we follow the original definition of the FR types (a division based solely on r), FR I and FR II RGs overlap in their host galaxy properties. However, the rare, LD sources with r>0.8 AND OIII5007 line luminosity >10^6 Lsun are markedly different on average from the rest of the RGs, in the sense that they are hosted in lower mass galaxies, live in relatively sparse environments, and have higher accretion rates onto the central SMBH. Thus these objects and the rest of RGs form a well-defined dichotomy. Motivated by the stark differences in the nuclear emission line properties of the RG subsamples, we suggest that the accretion rate onto the SMBH may play the primary role in creating the different morphologies. At relatively high accretion rates, the accretion system may produce powerful jets that create the "classical double" morphology (roughly corresponding to the LD sources with r>0.8 and emission lines); at lower accretion rates the jets from a radiatively inefficient accretion flow generate radio lobes without apparent "hot spots" at the edge (corresponding to the majority of LD sources). At slightly lower accretion rates AND in galaxies with dense galactic structure, sources with prominent jets result. It is possible that while the high accretion rate systems could affect sub-Mpc scale environments, the jets from lower accretion rate systems may efficiently suppress activity within the host galaxies.

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arXiv2010

The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectrum at 148 and 218 GHz from the 2008 Southern Survey

We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results clearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ΛCDM cosmological model. At l > 3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8σ level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

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arXiv2010

The Atacama Cosmology Telescope: Calibration with WMAP Using Cross-Correlations

We present a new calibration method based on cross-correlations with WMAP and apply it to data from the Atacama Cosmology Telescope (ACT). ACT's observing strategy and map making procedure allows an unbiased reconstruction of the modes in the maps over a wide range of multipoles. By directly matching the ACT maps to WMAP observations in the multipole range of 400 < ell < 1000, we determine the absolute calibration with an uncertainty of 2% in temperature. The precise measurement of the calibration error directly impacts the uncertainties in the cosmological parameters estimated from the ACT power spectra. We also present a combined map based on ACT and WMAP data that has high signal-to-noise over a wide range of multipoles.

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arXiv2010

A New Test of the Statistical Nature of the Brightest Cluster Galaxies

A novel statistic is proposed to examine the hypothesis that all cluster galaxies are drawn from the same luminosity distribution (LD). In such a "statistical model" of galaxy LD, the brightest cluster galaxies (BCGs) are simply the statistical extreme of the galaxy population. Using a large sample of nearby clusters, we show that BCGs in high luminosity clusters (e.g., L_tot > 4x10^11 L_sun) are unlikely (probability <3x10^-4) to be drawn from the LD defined by all red cluster galaxies more luminous than M_r=-20. On the other hand, BCGs in less luminous clusters are consistent with being the statistical extreme. Applying our method to the second brightest galaxies, we show that they are consistent with being the statistical extreme, which implies that the BCGs are also distinct from non-BCG luminous, red, cluster galaxies. We point out some issues with the interpretation of the classical tests proposed by Tremaine & Richstone (1977) that are designed to examine the statistical nature of BCGs, investigate the robustness of both our statistical test and those of TR against difficulties in photometry of galaxies of large angular size, and discuss the implication of our findings on surveys that use the luminous red galaxies to measure the baryon acoustic oscillation features in the galaxy power spectrum.

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arXiv2009

Simulations of the Microwave Sky

We create realistic, full-sky, half-arcminute resolution simulations of the microwave sky matched to the most recent astrophysical observations. The primary purpose of these simulations is to test the data reduction pipeline for the Atacama Cosmology Telescope (ACT) experiment; however, we have widened the frequency coverage beyond the ACT bands to make these simulations applicable to other microwave background experiments. Some of the novel features of these simulations are that the radio and infrared galaxy populations are correlated with the galaxy cluster populations, the CMB is lensed by the dark matter structure in the simulation via a ray-tracing code, the contribution to the thermal and kinetic Sunyaev-Zel'dovich (SZ) signals from galaxy clusters, groups, and the IGM has been included, and the gas prescription to model the SZ signals matches the most recent X-ray observations. Regarding the contamination of cluster SZ flux by radio galaxies, we find for 148 GHz (90 GHz) only 3% (4%) of halos have their SZ decrements contaminated at a level of 20% or more. We find the contamination levels higher for infrared galaxies. However, at 90 GHz, less than 20% of clusters with M_{200} > 2.5 x 10^{14} Msun and z<1.2 have their SZ decrements filled in at a level of 20% or more. At 148 GHz, less than 20% of clusters with M_{200} > 2.5 x 10^{14} Msun and z<0.8 have their SZ decrements filled in at a level of 50% or larger. Our models also suggest that a population of very high flux infrared galaxies, which are likely lensed sources, contribute most to the SZ contamination of very massive clusters at 90 and 148 GHz. These simulations are publicly available and should serve as a useful tool for microwave surveys to cross-check SZ cluster detection, power spectrum, and cross-correlation analyses.

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arXiv2009

Spectral Energy Distribution of Radio Sources in Nearby Clusters of Galaxies: Implications for Sunyaev-Zel'dovich Effect Surveys

To explore the high frequency radio spectra of galaxies in clusters, we used NRAO's Very Large Array at four frequencies, 4.9-43 GHz, to observe 139 galaxies in low redshift (z<0.25), X-ray detected, clusters. The clusters were selected from the survey conducted by Ledlow & Owen, who provided redshifts and 1.4 GHz flux densities for all the radio sources. We find that more than half of the observed sources have steep microwave spectra as generally expected (alpha<-0.5, in the convention S \propto nu^alpha). However, 60-70% of the unresolved or barely resolved sources have flat or inverted spectra. Most of these show an upward turn in flux at nu>22 GHz, implying a higher flux than would be expected from an extrapolation of the lower frequency flux measurements. Our results quantify the need for careful source subtraction in increasingly sensitive measurements of the Sunyaev-Zel'dovich effect in clusters of galaxies (as currently being conducted by, for instance, the Atacama Cosmology Telescope and South Pole Telescope groups).

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arXiv2008

Quasar Clustering from SDSS DR5: Dependences on Physical Properties

Using a homogenous sample of 38,208 quasars with a sky coverage of $4000 {\rm deg^2}$ drawn from the SDSS Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole mass, quasar color, and radio loudness. At $z<2.5$, quasar clustering depends weakly on luminosity and virial black hole mass, with typical uncertainty levels $\sim 10%$ for the measured correlation lengths. These weak dependences are consistent with models in which substantial scatter between quasar luminosity, virial black hole mass and the host dark matter halo mass has diluted any clustering difference, where halo mass is assumed to be the relevant quantity that best correlates with clustering strength. However, the most luminous and most massive quasars are more strongly clustered (at the $\sim 2σ$ level) than the remainder of the sample, which we attribute to the rapid increase of the bias factor at the high-mass end of host halos. We do not observe a strong dependence of clustering strength on quasar colors within our sample. On the other hand, radio-loud quasars are more strongly clustered than are radio-quiet quasars matched in redshift and optical luminosity (or virial black hole mass), consistent with local observations of radio galaxies and radio-loud type 2 AGN. Thus radio-loud quasars reside in more massive and denser environments in the biased halo clustering picture. Using the Sheth et al.(2001) formula for the linear halo bias, the estimated host halo mass for radio-loud quasars is $\sim 10^{13} h^{-1}M_\odot$, compared to $\sim 2\times 10^{12} h^{-1}M_\odot$ for radio-quiet quasar hosts at $z\sim 1.5$.

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arXiv2007

Luminous Red Galaxy Population in Clusters at $0.2\le z\le 0.6$

We investigate statistical properties of LRGs in a sample of X-ray selected galaxy clusters at intermediate redshift ($0.2\le z\le0.6$). The LRGs are selected based on carefully designed color criteria, and the cluster membership is assessed via photometric redshifts. As clusters and LRGs are both viewed as promising tracer of the underlying dark matter distribution, understanding the distribution of LRGs within clusters is an important issue. Our main findings include: 1. The halo occupation distribution of LRGs inside our cluster sample is $N(M) = k\times (M/10^{14})^{a}$ where $a=0.620\pm 0.105 $ and $k=1.425\pm0.285 $ assuming a Poisson distribution for $N(M)$. 2. The halo occupation distribution of LRGs ($N(M)$) and the satellite distribution of LRGs ($N-1(M)$) are both consistent with being Poisson. To be more quantitative, we find $Var(N)/ = 1.428\pm 0.351$ and $Var(N-1)/ = 1.823 \pm 0.496$ 3. The radial profile of LRGs within clusters when fitted with a NFW profile gives a concentration of $17.5^{+7.1}_{-4.3}$ ($6.0^{+3.2}_{-1.9}$) including (excluding) BLRGs (Brightest LRGs). We also discuss the implications of these observations on the evolution of massive galaxies in clusters.

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arXiv2007

Missing Thermal Energy of the Intracluster Medium

The Sunyaev-Zel'dovich (SZ) effect is a direct probe of thermal energy content of the Universe, induced in the cosmic microwave background (CMB) sky through scattering of CMB photons off hot electrons in the intracluster medium (ICM). We report a 9-sigma detection of the SZ signal in the CMB maps of Wilkinson Microwave Anisotropy Probe (WMAP) 3yr data, through study of a sample of 193 massive galaxy clusters with observed X-ray temperatures greater than 3 keV. For the first time, we make a model-independent measurement of the pressure profile in the outskirts of the ICM, and show that it closely follows the profiles obtained by X-ray observations and numerical simulations. We find that our measurements of the SZ effect would account for only half of the thermal energy of the cluster, if all the cluster baryons were in the hot ICM phase. Our measurements indicate that a significant fraction (35 +/- 8 %) of baryonic mass is missing from the hot ICM, and thus must have cooled to form galaxies, intracluster stars, or an unknown cold phase of the ICM. There does not seem to be enough mass in the form of stars or cold gas in the cluster galaxies or intracluster space, signaling the need for a yet-unknown baryonic component (at 3-sigma level), or otherwise new astrophysical processes in the ICM.

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arXiv2007

Radio Sources in Galaxy Clusters: Radial Distribution, and 1.4 GHz and K-band Bivariate Luminosity Function

We present a statistical study of several fundamental properties of radio sources in nearby clusters, including the radial distribution within clusters, the radio luminosity function (RLF), and the fraction of galaxies that is radio-active (radio active fraction, RAF). The analysis is carried out for a sample of 573 clusters detected in the X-ray and also observed at 1.4 GHz in the NVSS. K-band data from the 2MASS are used to identify the brightest cluster galaxies (BCGs), and to construct the K-band LF. Our main results include: (1) The surface density profile of radio-loud AGNs is much more concentrated than that of all galaxies, and can be described by the NFW profile with concentration ~ 25. (2) A comparison of the RLFs in the clusters and in the field shows that the cluster AGN number density is about 5,700 times higher, corresponding to a factor of 6.8 higher probability of a galaxy being radio active in the cluster than in the field. We suggest that about 40-50% of radio-loud AGNs in clusters may reside in low mass galaxies (M_K>-23). (3) The RAFs of cluster galaxies of different stellar mass are estimated. About 5% of galaxies more luminous than the characteristic luminosity (M_K 30%, and depends on the cluster mass. Compare to the field population, cluster galaxies have 5-10 times higher RAF. Combining the AGN RLF and spatial distribution within clusters, we estimate that they may inject an energy of ~0.13 keV per particle to the intracluster medium near the cluster center. We also investigate the degree of contamination by cluster radio sources on the yields of SZE cluster surveys, and estimate that as many as 10% of clusters detected at 150 GHz may host AGNs whose flux is comparable to the cluster SZE signal. (abridged)

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arXiv2006

Evolution of the K-band Galaxy Cluster Luminosity Function and Scaling Relations

We study the evolution of two fundamental properties of galaxy clusters: the luminosity function (LF) and the scaling relations between the total galaxy number N (or luminosity) and cluster mass M. Using a sample of 27 clusters (0<z<0.9) with new near-IR observations and mass estimates derived from X-ray temperatures, in conjunction with data from the literature, we construct the largest sample for such studies to date. The evolution of the characteristic luminosity of the LF can be described by a passively evolving population formed in a single burst at z=1.5-2. Under the assumption that the mass-temperature relation evolves self-similarly, and after the passive evolution is accounted for, the N-M scaling shows no signs of evolution out to z=0.9. Our data provide direct constraints on halo occupation distribution models, and suggest that the way galaxies populate cluster-scale dark matter halos has not changed in the past 7 Gyr, in line with previous investigations.

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arXiv2005

A Beginner's Guide to the Theory of CMB Temperature and Polarization Power Spectra in the Line-of-Sight Formalism

We present here a detailed, self--contained treatment of the mathematical formalism for describing the theory of polarized anisotropy in the cosmic microwave background. This didactic review is aimed at researchers who are new to the field. We first develop the mathematical tools for describing polarized scattering of CMB photons. Then we take the reader through a detailed derivation of the line-of-sight formalism, explaining the calculation of both temperature and polarization power spectra due to the scalar and tensor perturbations in a flat Universe.

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arXiv2005

The FLAMINGOS Extragalactic Survey

Using the Florida Multi-object Imaging Near-IR grism Observational Spectrometer (FLAMINGOS), we have conducted the FLAMINGOS Extragalactic Survey (FLAMEX), a deep imaging survey covering 7.1 square degrees within the 18.6 sq. deg NOAO Deep Wide-Field Survey (NDWFS) regions. FLAMEX is the first deep, wide-area near-infrared survey to image in both the J and Ks filters, and is larger than any previous NIR surveys of comparable depth. The intent of FLAMEX is to facilitate the study of galaxy and galaxy cluster evolution at 1 1 galaxy clusters detected using the joint FLAMEX, NDWFS, and Spitzer IRAC Shallow Survey data sets.

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arXiv2005

WMAP constraints on the Intra-Cluster Medium

We devise a Monte-Carlo based, optimized filter match method to extract the thermal Sunyaev-Zel'dovich (SZ) signature of a catalog of 116 low-redshift X-ray clusters from the first year data release of the Wilkinson Microwave Anisotropy Probe (WMAP). We detect an over-all amplitude for the SZ signal at the ~ 8-sigma level, yielding a combined constraint of f_{gas}h = 0.08 +/- 0.01 (ran) +/- 0.01 (sys) on the gas mass fraction of the Intra-Cluster Medium. We also compile X-ray estimated gas fractions from the literature for our sample, and find that they are consistent with the SZ estimates at the 2-sigma level, while both show an increasing trend with X-ray temperature. Nevertheless, our SZ estimated gas fraction is 30-40% smaller than the concordance LCDM cosmic average. We also express our observations in terms of the SZ flux-temperature relation, and compare it with other observations, as well as numerical studies. Based on its spectral and spatial signature, we can also extract the microwave point source signal of the clusters at the 3-sigma level, which puts the average microwave luminosity (at ~ 41 GHz) of bright cluster members (M_K < -21) at (2.4 +/- 0.8) x 10^{27} h^{-2} erg/s/Hz. Furthermore, we can constrain the average dark matter halo concentration parameter to c_{vir}=3.4+0.6-0.9, for clusters with T_x > 5 kev. Our work serves as an example for how correlation of SZ surveys with cluster surveys in other frequencies can significantly increase our physical understanding of the intra-cluster medium.

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