Bayesian High-Redshift Quasar Classification from Optical and Mid-IR Photometry

We identify 885,503 type 1 quasar candidates to i<22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-Field Infrared Survey Explorer (WISE) "ALLWISE" data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically-confirmed type-1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high probability potential quasars with 3.5<z<5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z>3.5 than the traditional mid-IR selection "wedges" and to 2.2<z<3.5 quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggests that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z>3. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.Comment: 54 pages, 17 figures; accepted by ApJS Data for tables 1 and 2 available at http://www.physics.drexel.edu/~gtr/outgoing/optirqsos/data/master_quasar_catalogs.011414.fits.bz2 and http://www.physics.drexel.edu/~gtr/outgoing/optirqsos/data/optical_ir_quasar_candidates.052015.fits.bz

The Ultraviolet-to-Mid-Infrared Spectral Energy Distribution of Weak Emission Line Quasars

We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey (SDSS) quasars at 2.7 <= z <= 5.9 which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet (UV) spectra (hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with SDSS spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame ~0.1-5 mum spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line-of-sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.Comment: 10 pages (emulateapj), 4 figures. Accepted for publication in Ap

CANDELS: The progenitors of compact quiescent galaxies at z~2

We combine high-resolution HST/WFC3 images with multi-wavelength photometry to track the evolution of structure and activity of massive (log(M*) > 10) galaxies at redshifts z = 1.4 - 3 in two fields of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). We detect compact, star-forming galaxies (cSFGs) whose number densities, masses, sizes, and star formation rates qualify them as likely progenitors of compact, quiescent, massive galaxies (cQGs) at z = 1.5 - 3. At z > 2 most cSFGs have specific star-formation rates (sSFR = 10^-9 yr^-1) half that of typical, massive SFGs at the same epoch, and host X-ray luminous AGN 30 times (~30%) more frequently. These properties suggest that cSFGs are formed by gas-rich processes (mergers or disk-instabilities) that induce a compact starburst and feed an AGN, which, in turn, quench the star formation on dynamical timescales (few 10^8 yr). The cSFGs are continuously being formed at z = 2 - 3 and fade to cQGs by z = 1.5. After this epoch, cSFGs are rare, thereby truncating the formation of new cQGs. Meanwhile, down to z = 1, existing cQGs continue to enlarge to match local QGs in size, while less-gas-rich mergers and other secular mechanisms shepherd (larger) SFGs as later arrivals to the red sequence. In summary, we propose two evolutionary scenarios of QG formation: an early (z > 2), fast-formation path of rapidly-quenched cSFGs that evolve into cQGs that later enlarge within the quiescent phase, and a slow, late-arrival (z < 2) path for SFGs to form QGs without passing through a compact state.Comment: Submitted to the Astrophysical Journal Letters, 6 pages, 4 figure

A CANDELS WFC3 Grism Study of Emission-Line Galaxies at z~2: A Mix of Nuclear Activity and Low-Metallicity Star Formation

We present Hubble Space Telescope Wide Field Camera 3 slitless grism spectroscopy of 28 emission-line galaxies at z~2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). The high sensitivity of these grism observations, with 1-sigma detections of emission lines to f > 2.5x10^{-18} erg/s/cm^2, means that the galaxies in the sample are typically ~7 times less massive (median M_* = 10^{9.5} M_sun) than previously studied z~2 emission-line galaxies. Despite their lower mass, the galaxies have OIII/Hb ratios which are very similar to previously studied z~2 galaxies and much higher than the typical emission-line ratios of local galaxies. The WFC3 grism allows for unique studies of spatial gradients in emission lines, and we stack the two-dimensional spectra of the galaxies for this purpose. In the stacked data the OIII emission line is more spatially concentrated than the Hb emission line with 98.1 confidence. We additionally stack the X-ray data (all sources are individually undetected), and find that the average L(OIII)/L(0.5-10 keV) ratio is intermediate between typical z~0 obscured active galaxies and star-forming galaxies. Together the compactness of the stacked OIII spatial profile and the stacked X-ray data suggest that at least some of these low-mass, low-metallicity galaxies harbor weak active galactic nuclei.Comment: ApJ accepted. 8 pages, 6 figure

The Sloan Digital Sky Survey Reverberation Mapping Project: Key Results

We present the final data from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project, a precursor to the SDSS-V Black Hole Mapper Reverberation Mapping program. This data set includes 11-year photometric and 7-year spectroscopic light curves for 849 broad-line quasars over a redshift range of 0.1<z<4.5 and a luminosity range of Lbol=1E44-47.5 erg/s, along with spectral and variability measurements. We report 23, 81, 125, and 110 reverberation mapping lags (relative to optical continuum variability) for broad Halpha, Hbeta, MgII and CIV using the SDSS-RM sample, spanning much of the luminosity and redshift ranges of the sample. Using 30 low-redshift RM AGNs with dynamical-modeling black hole masses, we derive a new estimate of the average virial factor of =0.62+-0.07 for the line dispersion measured from the RMS spectrum. The intrinsic scatter of individual virial factors is 0.31+-0.07 dex, indicating a factor of two systematic uncertainty in RM black hole masses. Our lag measurements reveal significant R-L relations for Hbeta and MgII at high redshift, consistent with the latest measurements based on heterogeneous samples. While we are unable to robustly constrain the slope of the R-L relation for CIV given the limited dynamical range in luminosity, we found substantially larger scatter in CIV lags at fixed L1350. Using the SDSS-RM lag sample, we derive improved single-epoch (SE) mass recipes for Hbeta, MgII and CIV, which are consistent with their respective RM masses as well as between the SE recipes from two different lines, over the luminosity range probed by our sample. The new Hbeta and MgII recipes are approximately unbiased estimators at given RM masses, but there are systematic biases in the CIV recipe. The intrinsic scatter of SE masses around RM masses is ~0.45 dex for Hbeta and MgII, increasing to ~0.58 dex for CIV.Comment: 33 pages. Data products available at ftp://quasar.astro.illinois.edu/public/sdssrm/final_result

The Sloan Digital Sky Survey Reverberation Mapping project : key results

Funding: Y.S. acknowledges support from NSF grants AST-1715579 and AST-2009947. C.J.G. acknowledges support from NSF grants AST-2009949 and AST-2108667. J.I.L. is supported by the Eric and Wendy Schmidt AI in Science Postdoctoral Fellowship, a Schmidt Futures program. Y.H. was supported as an Eberly Research Fellow by the Eberly College of Science at the Pennsylvania State University. J.R.T. acknowledges support from NSF grants CAREER-1945546, AST-2009539, and AST-2108668. W.N.B. acknowledges support from NSF grant AST-2106990 and the Eberly Endowment at Penn State. L.C.H. was supported by the National Science Foundation of China (11721303, 11991052, 12011540375, 12233001) and the China Manned Space Project (CMS-CSST-2021-A04, CMS-CSST-2021-A06). C.T. acknowledges Tsinghua University for the support to her work.We present the final data from the Sloan Digital Sky Survey (SDSS) Reverberation Mapping (RM) project, a precursor to the SDSS-V Black Hole Mapper RM program. This data set includes 11 yr photometric and 7 yr spectroscopic light curves for 849 broad-line quasars over a redshift range of 0.1 < z < 4.5 and a luminosity range of Lbol = 1044−47.5 erg s−1, along with spectral and variability measurements. We report 23, 81, 125, and 110 RM lags (relative to optical continuum variability) for broad Hα, Hβ, Mg ii, and C iv using the SDSS-RM sample, spanning much of the luminosity and redshift ranges of the sample. Using 30 low-redshift RM active galactic nuclei with dynamical-modeling black hole masses, we derive a new estimate of the average virial factor of ⟨logf⟩ = 0.62±0.07 for the line dispersion measured from the rms spectrum. The intrinsic scatter of individual virial factors is 0.31 ± 0.07 dex, indicating a factor of 2 systematic uncertainty in RM black hole masses. Our lag measurements reveal significant R–L relations for Hβ and Mg ii at high redshift, consistent with the latest measurements based on heterogeneous samples. While we are unable to robustly constrain the slope of the R–L relation for C iv given the limited dynamic range in luminosity, we found substantially larger scatter in C iv lags at fixed L1350. Using the SDSS-RM lag sample, we derive improved single-epoch (SE) mass recipes for Hβ, Mg ii, and C iv, which are consistent with their respective RM masses as well as between the SE recipes from two different lines, over the luminosity range probed by our sample. The new Hβ and Mg ii recipes are approximately unbiased estimators at given RM masses, but there are systematic biases in the C iv recipe. The intrinsic scatter of SE masses around RM masses is ∼0.45 dex for Hβ and Mg ii, increasing to ∼0.58 dex for C iv.Peer reviewe

The MOSDEF survey:AGN multi-wavelength identification, selection biases and host galaxy properties

We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR and optically-selected active galactic nuclei (AGN) at $1.4 < z < 3.8$. We obtain rest-frame optical spectra of galaxies and AGN and use the BPT diagram to identify optical AGN. We examine the uniqueness and overlap of the AGN identified at different wavelengths. There is a strong bias against identifying AGN at any wavelength in low mass galaxies, and an additional bias against identifying IR AGN in the most massive galaxies. AGN hosts span a wide range of star formation rate (SFR), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we find (at $\sim 2-3\sigma$ significance) that IR AGN are in less dusty galaxies with relatively higher SFR and optical AGN in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at lower redshifts. Within star-forming galaxies, once selection biases are accounted for, we find AGN in galaxies with similar physical properties as inactive galaxies, with no evidence for AGN activity in particular types of galaxies. This is consistent with AGN being fueled stochastically in any star-forming host galaxy. We do not detect a significant correlation between SFR and AGN luminosity for individual AGN hosts, which may indicate the timescale difference between the growth of galaxies and their supermassive black holes

Evaluation of individual and ensemble probabilistic forecasts of COVID-19 mortality in the United States

Short-term probabilistic forecasts of the trajectory of the COVID-19 pandemic in the United States have served as a visible and important communication channel between the scientific modeling community and both the general public and decision-makers. Forecasting models provide specific, quantitative, and evaluable predictions that inform short-term decisions such as healthcare staffing needs, school closures, and allocation of medical supplies. Starting in April 2020, the US COVID-19 Forecast Hub (https://covid19forecasthub.org/) collected, disseminated, and synthesized tens of millions of specific predictions from more than 90 different academic, industry, and independent research groups. A multimodel ensemble forecast that combined predictions from dozens of groups every week provided the most consistently accurate probabilistic forecasts of incident deaths due to COVID-19 at the state and national level from April 2020 through October 2021. The performance of 27 individual models that submitted complete forecasts of COVID-19 deaths consistently throughout this year showed high variability in forecast skill across time, geospatial units, and forecast horizons. Two-thirds of the models evaluated showed better accuracy than a naïve baseline model. Forecast accuracy degraded as models made predictions further into the future, with probabilistic error at a 20-wk horizon three to five times larger than when predicting at a 1-wk horizon. This project underscores the role that collaboration and active coordination between governmental public-health agencies, academic modeling teams, and industry partners can play in developing modern modeling capabilities to support local, state, and federal response to outbreaks