- ID:
- ivo://CDS.VizieR/J/ApJS/250/10
- Title:
- SDSS-RM AGNs CFHT & Bok photometry over 4yrs
- Short Name:
- J/ApJS/250/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey (SDSS) Reverberation Mapping program monitors 849 active galactic nuclei (AGNs) both spectroscopically and photometrically. The photometric observations used in this work span over 4yr and provide an excellent baseline for variability studies of these objects. We present the photometric light curves from 2014 to 2017 obtained by the Steward Observatory's Bok telescope and the Canada-France-Hawaii telescope with MegaCam. We provide details on the data acquisition and processing of the data from each telescope, the difference imaging photometry used to produce the light curves, and the calculation of a variability index to quantify each AGN's variability. We find that the Welch-Stetson J index provides a useful characterization of AGN variability and can be used to select AGNs for further study.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/887/38
- Title:
- SDSS RM Project: CIV lags & LCs from 4yrs of data
- Short Name:
- J/ApJ/887/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present reverberation-mapping (RM) lags and black hole mass measurements using the CIV{lambda}1549 broad emission line from a sample of 348 quasars monitored as a part of the Sloan Digital Sky Survey RM Project. Our data span four years of spectroscopic and photometric monitoring for a total baseline of 1300 days, allowing us to measure lags up to ~750days in the observed frame (this corresponds to a rest-frame lag of ~300days in a quasar at z=1.5 and ~190days at z=3). We report significant time delays between the continuum and the CIV{lambda}1549 emission line in 48 quasars, with an estimated false-positive detection rate of 10%. Our analysis of marginal lag measurements indicates that there are on the order of ~100 additional lags that should be recoverable by adding more years of data from the program. We use our measurements to calculate black hole masses and fit an updated CIV radius-luminosity relationship. Our results significantly increase the sample of quasars with CIV RM results, with the quasars spanning two orders of magnitude in luminosity toward the high-luminosity end of the CIV radius-luminosity relation. In addition, these quasars are located at some of the highest redshifts (z~1.4-2.8) of quasars with black hole masses measured with RM.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/126
- Title:
- SDSS RM project: continuum lags
- Short Name:
- J/ApJ/880/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accretion disk structure measurements from continuum lags in the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. Lags are measured using the JAVELIN software from the first-year SDSS-RM g and i photometry, resulting in well-defined lags for 95 quasars, 33 of which have lag S/N>2{sigma}. We also estimate lags using the ICCF software and find consistent results, though with larger uncertainties. Accretion disk structure is fit using a Markov chain Monte Carlo approach, parameterizing the measured continuum lags as a function of disk size normalization, wavelength, black hole mass, and luminosity. In contrast with previous observations, our best-fit disk sizes and color profiles are consistent (within 1.5{sigma}) with the Shakura & Sunyaev (1973A&A....24..337S) analytic solution. We also find that more massive quasars have larger accretion disks, similarly consistent with the analytic accretion disk model. The data are inconclusive on a correlation between disk size and continuum luminosity, with results that are consistent with both no correlation and the Shakura & Sunyaev expectation. The continuum lag fits have a large excess dispersion, indicating that our measured lag errors are underestimated and/or our best-fit model may be missing the effects of orientation, spin, and/or radiative efficiency. We demonstrate that fitting disk parameters using only the highest-S/N lag measurements biases best-fit disk sizes to be larger than the disk sizes recovered using a Bayesian approach on the full sample of well-defined lags.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/21
- Title:
- SDSS RM project first year of observations
- Short Name:
- J/ApJ/851/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present reverberation mapping results from the first year of combined spectroscopic and photometric observations of the Sloan Digital Sky Survey Reverberation Mapping Project. We successfully recover reverberation time delays between the g+i band emission and the broad H{beta} emission line for a total of 44 quasars, and for the broad H{alpha} emission line in 18 quasars. Time delays are computed using the JAVELIN and CREAM software and the traditional interpolated cross-correlation function (ICCF): using well-defined criteria, we report measurements of 32 H{beta} and 13 H{alpha} lags with JAVELIN, 42 H{beta} and 17 H{alpha} lags with CREAM, and 16 H{beta} and eight H{alpha} lags with the ICCF. Lag values are generally consistent among the three methods, though we typically measure smaller uncertainties with JAVELIN and CREAM than with the ICCF, given the more physically motivated light curve interpolation and more robust statistical modeling of the former two methods. The median redshift of our H{beta}-detected sample of quasars is 0.53, significantly higher than that of the previous reverberation mapping sample. We find that in most objects, the time delay of the H{alpha} emission is consistent with or slightly longer than that of H{beta}. We measure black hole masses using our measured time delays and line widths for these quasars. These black hole mass measurements are mostly consistent with expectations based on the local M_BH_-{sigma}* relationship, and are also consistent with single-epoch black hole mass measurements. This work increases the current sample size of reverberation-mapped active galaxies by about two- thirds and represents the first large sample of reverberation mapping observations beyond the local universe (z<0.3).
- ID:
- ivo://CDS.VizieR/J/ApJ/882/4
- Title:
- SDSS-RM project: H{alpha}, H{beta} & MgII lines
- Short Name:
- J/ApJ/882/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The width of the broad emission lines in quasars is commonly characterized by either the FWHM or the square root of the second moment of the line profile ({sigma}line) and used as an indicator of the virial velocity of the broad-line region (BLR) in the estimation of black hole (BH) mass. We measure FWHM and {sigma}line for H{alpha}, H{beta}, and MgII broad lines in both the mean and rms spectra of a large sample of quasars from the Sloan Digital Sky Survey Reverberation Mapping project. We introduce a new quantitative recipe to measure {sigma}line that is reproducible, is less susceptible to noise and blending in the wings, and scales with the intrinsic width of the line. We compare the four definitions of line width (FWHM and {sigma}line in mean and rms spectra, respectively) for each of the three broad lines and among different lines. There are strong correlations among different width definitions for each line, providing justification for using the line width measured in single-epoch spectroscopy as a virial velocity indicator. There are also strong correlations among different lines, suggesting that alternative lines to H{beta} can be used to estimate virial BH masses. We further investigate the correlations between virial BH masses using different line width definitions and the stellar velocity dispersion of the host galaxies and the dependence of line shape (characterized by the ratio FWHM/{sigma}line) on physical properties of the quasar. Our results provide further evidence that FWHM is more sensitive to the orientation of a flattened BLR geometry than {sigma}line, but the overall comparison between the virial BH mass and host stellar velocity dispersion does not provide conclusive evidence that one particular width definition is significantly better than the others.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/7
- Title:
- SDSS-RM project: peak velocities of QSOs
- Short Name:
- J/ApJ/831/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasar emission lines are often shifted from the systemic velocity due to various dynamical and radiative processes in the line-emitting region. The level of these velocity shifts depends both on the line species and on quasar properties. We study velocity shifts for the line peaks (not the centroids) of various narrow and broad quasar emission lines relative to systemic using a sample of 849 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The coadded (from 32 epochs) spectra of individual quasars have sufficient signal-to-noise ratio (S/N) to measure stellar absorption lines to provide reliable systemic velocity estimates, as well as weak narrow emission lines. The large dynamic range in quasar luminosity (~2dex) of the sample allowed us to explore potential luminosity dependence of the velocity shifts. We derive average line peak velocity shifts as a function of quasar luminosity for different lines, and quantify their intrinsic scatter. We further quantify how well the peak velocity can be measured as a function of continuum S/N, and demonstrate that there is no systematic bias in the velocity measurements when S/N is degraded to as low as ~3 per SDSS pixel (~69kms/s). Based on the observed line shifts, we provide empirical guidelines on redshift estimation from [OII]{lambda}3727, [OIII]{lambda}5007, [NeV]{lambda}3426, MgII, CIII], HeII{lambda}1640, broad H{beta}, CIV, and SiIV, which are calibrated to provide unbiased systemic redshifts in the mean, but with increasing intrinsic uncertainties of 46, 56, 119, 205, 233, 242, 400, 415, and 477kms/s, in addition to the measurement uncertainties. These results demonstrate the infeasibility of measuring quasar redshifts to better than ~200kms/s with only broad lines.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/4
- Title:
- SDSS-RM project: technical overview
- Short Name:
- J/ApJS/216/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project is a dedicated multi-object RM experiment that has spectroscopically monitored a sample of 849 broad-line quasars in a single 7deg^2^ field with the SDSS-III Baryon Oscillation Spectroscopic Survey spectrograph. The RM quasar sample is flux-limited to i_psf_=21.7mag, and covers a redshift range of 0.1<z<4.5 without any other cuts on quasar properties. Optical spectroscopy was performed during 2014 January-July dark/gray time, with an average cadence of ~4 days, totaling more than 30 epochs. Supporting photometric monitoring in the g and i bands was conducted at multiple facilities including the Canada-France-Hawaii Telescope (CFHT) and the Steward Observatory Bok telescope in 2014, with a cadence of ~2 days and covering all lunar phases. The RM field (RAJ2000=14:14:49.00, DEJ2000=+53:05:00.0) lies within the CFHT-LS W3 field, and coincides with the Pan-STARRS 1 (PS1) Medium Deep Field MD07, with three prior years of multi-band PS1 light curves. The SDSS-RM six month baseline program aims to detect time lags between the quasar continuum and broad line region (BLR) variability on timescales of up to several months (in the observed frame) for ~10% of the sample, and to anchor the time baseline for continued monitoring in the future to detect lags on longer timescales and at higher redshift. SDSS-RM is the first major program to systematically explore the potential of RM for broad-line quasars at z>0.3, and will investigate the prospects of RM with all major broad lines covered in optical spectroscopy.
- ID:
- ivo://CDS.VizieR/J/ApJ/811/91
- Title:
- SDSS-RM project: z<1 QSO host galaxies
- Short Name:
- J/ApJ/811/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasar host galaxies are key for understanding the relation between galaxies and the supermassive black holes (SMBHs) at their centers. We present a study of 191 broad-line quasars and their host galaxies at z<1 using high signal-to-noise ratio (S/N) spectra produced by the Sloan Digital Sky Survey Reverberation Mapping project. Clear detection of stellar absorption lines allows a reliable decomposition of the observed spectra into nuclear and host components, using spectral models of quasar and stellar radiations as well as emission lines from the interstellar medium. We estimate age, mass M*, and velocity dispersion {sigma}* of the host stars, the star formation rate (SFR), quasar luminosity, and SMBH mass M_{dot}_ for each object. The quasars are preferentially hosted by massive galaxies with M*~10^11^M_{sun}_ characterized by stellar ages around 1 billion yr, which coincides with the transition phase of normal galaxies from the blue cloud to the red sequence. The host galaxies have relatively low SFRs and fall below the main sequence of star-forming galaxies at similar redshifts. These facts suggest that the hosts have experienced an episode of major star formation sometime in the past 1 billion yr, which was subsequently quenched or suppressed. The derived M_{dot}_-{sigma}* and M_{dot}_-M* relations agree with our past measurements and are consistent with no evolution from the local universe. The present analysis demonstrates that reliable measurements of stellar properties of quasar host galaxies are possible with high-S/N fiber spectra, which will be acquired in large numbers with future powerful instruments such as the Subaru Prime Focus Spectrograph.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/1
- Title:
- SDSS-Spitzer AGN properties
- Short Name:
- J/ApJ/758/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from the Sloan Digital Sky Survey (SDSS) and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic contributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [Ne II] 12.8{mu}m emission line is well correlated with the star formation rate measured from the SDSS spectra, and this holds for the star-forming, composite, and AGN-dominated systems. AGNs show a clear excess of [Ne III] 15.6{mu}m emission relative to star-forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including the mid-IR spectral slope, the ratio of the [Ne V] 14.3{mu}m to [Ne II] 12.8{mu}m fluxes, the equivalent widths of the 7.7{mu}m, 11.3{mu}m, and 17{mu}m polycyclic aromatic hydrocarbon (PAH) features, and the optical "D" parameter which measures the distance at which a source lies from the locus of star-forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN dominance. We find that the PAH 11.3{mu}m feature is significantly suppressed in the most AGN-dominated systems.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/470
- Title:
- SDSS-Spitzer type I QSOs IR photometry
- Short Name:
- J/ApJS/166/470
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z~3, with predictions to z=7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available.
