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A Transient “Changing-look” Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
We report the discovery of a new “changing-look” active galactic nucleus (CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z = 0.2603, identified through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V). Optical photometry taken during 2020-2021 shows a dramatic dimming of Δg ≈ 1 mag, followed by a rapid recovery on a timescale of several months, with the ≲2 month period of rebrightening captured in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the fastest CLAGN transitions observed to date. Archival observations suggest that the object experienced a much more gradual dimming over the period of 2011-2013. Our spectroscopy shows that the photometric changes were accompanied by dramatic variations in the quasar-like continuum and broad-line emission. The excellent agreement between the pre- and postdip photometric and spectroscopic appearances of the source, as well as the fact that the dimmest spectra can be reproduced by applying a single extinction law to the brighter spectral states, favor a variable line-of-sight obscuration as the driver of the observed transitions. Such an interpretation faces several theoretical challenges, and thus an alternative accretion-driven scenario cannot be excluded. The recent events observed in this quasar highlight the importance of spectroscopic monitoring of large active galactic nucleus samples on weeks-to-months timescales, which the SDSS-V is designed to achieve
A Transient "Changing-look'' Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
We report the discovery of a new ``changing-look'' active galactic nucleus
(CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z=0.2603, identified
through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V).
Optical photometry taken during 2020--2021 shows a dramatic dimming of
g1 mag, followed by a rapid recovery on a timescale of
several months, with the 2 month period of rebrightening captured
in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the
fastest CLAGN transitions observed to date. Archival observations suggest that
the object experienced a much more gradual dimming over the period of
2011--2013. Our spectroscopy shows that the photometric changes were
accompanied by dramatic variations in the quasar-like continuum and broad-line
emission. The excellent agreement between the pre- and postdip photometric and
spectroscopic appearances of the source, as well as the fact that the dimmest
spectra can be reproduced by applying a single extinction law to the brighter
spectral states, favor a variable line-of-sight obscuration as the driver of
the observed transitions. Such an interpretation faces several theoretical
challenges, and thus an alternative accretion-driven scenario cannot be
excluded. The recent events observed in this quasar highlight the importance of
spectroscopic monitoring of large active galactic nucleus samples on
weeks-to-months timescales, which the SDSS-V is designed to achieve.Comment: Published in ApJ
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 eighteenth data release of the Sloan Digital Sky Surveys : targeting and first spectra from SDSS-V
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains extensive targeting information for the two multi-object spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration- and scientifically-focused components. DR18 also includes ~25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.Publisher PDFPeer reviewe
The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. It pursues three core programs: APOGEE-2,MaNGA, and eBOSS. In addition, eBOSS contains two major subprograms: TDSS and SPIDERS. This paper describes the first data release from SDSS-IV, Data Release 13 (DR13), which contains new data, reanalysis of existing data sets and, like all SDSS data releases, is inclusive of previously released data. DR13 makes publicly available 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA,the first data released from this survey. It includes new observations from eBOSS, completing SEQUELS. In addition to targeting galaxies and quasars, SEQUELS also targeted variability-selected objects from TDSS and X-ray selected objects from SPIDERS. DR13 includes new reductions ofthe SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification. DR13 releases new reductions of the APOGEE-1data from SDSS-III, with abundances of elements not previously included and improved stellar parameters for dwarf stars and cooler stars. For the SDSS imaging data, DR13 provides new, more robust and precise photometric calibrations. Several value-added catalogs are being released in tandem with DR13, in particular target catalogs relevant for eBOSS, TDSS, and SPIDERS, and an updated red-clump catalog for APOGEE.This paper describes the location and format of the data now publicly available, as well as providing references to the important technical papers that describe the targeting, observing, and data reduction. The SDSS website, http://www.sdss.org, provides links to the data, tutorials and examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ~6-year operations of SDSS-IV.PostprintPeer reviewe
The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA-derived Quantities, Data Visualization Tools, and Stellar Library
Twenty years have passed since first light for the Sloan Digital Sky Survey (SDSS). Here, we release data taken by the fourth phase of SDSS (SDSS-IV) across its first three years of operation (2014 July–2017 July). This is the third data release for SDSS-IV, and the 15th from SDSS (Data Release Fifteen; DR15). New data come from MaNGA—we release 4824 data cubes, as well as the first stellar spectra in the MaNGA Stellar Library (MaStar), the first set of survey-supported analysis products (e.g., stellar and gas kinematics, emission-line and other maps) from the MaNGA Data Analysis Pipeline, and a new data visualization and access tool we call "Marvin." The next data release, DR16, will include new data from both APOGEE-2 and eBOSS; those surveys release no new data here, but we document updates and corrections to their data processing pipelines. The release is cumulative; it also includes the most recent reductions and calibrations of all data taken by SDSS since first light. In this paper, we describe the location and format of the data and tools and cite technical references describing how it was obtained and processed. The SDSS website (www.sdss.org) has also been updated, providing links to data downloads, tutorials, and examples of data use. Although SDSS-IV will continue to collect astronomical data until 2020, and will be followed by SDSS-V (2020–2025), we end this paper by describing plans to ensure the sustainability of the SDSS data archive for many years beyond the collection of data
Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median ). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July