We present and make publicly available the second data release (DR2) of the Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey. KODIAQ DR2 consists of a fully reduced sample of 300 quasars at 0.07<z_em_<5.29 observed with HIRES at high resolution (36000{<=}R{<=}103000). DR2 contains 831 spectra available in continuum normalized form, representing a sum total exposure time of ~4.9 megaseconds on source. These co-added spectra arise from a total of 1577 individual exposures of quasars taken from the Keck Observatory Archive (KOA) in raw form and uniformly processed. DR2 extends DR1 by adding 130 new quasars to the sample, including additional observations of QSOs in DR1. All new data in DR2 were obtained with the single-chip Tektronix TK2048 CCD configuration of HIRES in operation between 1995 and 2004. DR2 is publicly available to the community, housed as a higher level science product at the KOA and in the igmspec database (v03).
We present and make publicly available the third data release (DR3) of the Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey. KODIAQ DR3 consists of a fully reduced sample of 727 quasars at 0.1<zem<6.4 observed with the Echellette Sepctrograph and Imager at moderate resolution (4000<~R<~10000). DR3 contains 872 spectra available in flux calibrated form, representing a sum total exposure time of ~2.8 megaseconds. These coadded spectra arise from a total of 2753 individual exposures of quasars taken from the Keck Observatory Archive (KOA) in raw form and uniformly processed using a data reduction package made available through the XIDL distribution. DR3 is publicly available to the community, housed as a higher level science product at the KOA and in the igmspec database.
Large spectroscopic surveys have discovered very peculiar and hitherto unknown types of active galactic nuclei (AGN). Such rare objects may hold clues to the accretion history of the supermassive black holes at the centres of galaxies. We aim to create a sizeable sample of unusual quasars from the unprecedented spectroscopic database of the Sloan Digital Sky Survey (SDSS).
We previously reported a significant clustering of red galaxies (R-K=3.56) around the radio-loud quasar B2 1335+28 at z=1.086. In this paper, we establish the existence of a rich cluster at the quasar redshift and study the properties of the cluster galaxies through further detailed analysis of the photometric data. We also list the positions, K-band magnitudes, and colors of all K<19 objects. The near-infrared (NIR) K-band imaging data presented in earlier paper, together with some additional K-band data, is newly analyzed to study the extent of the clustering of the red galaxies. We also constrain the cluster redshift by applying a robust photometric redshift estimator and find a strong peak around z=1.1. The color distribution of the galaxies in the cluster is quite broad, and the fraction of blue galaxies (70%) is much larger than in intermediate-redshift clusters.
In this paper we present preliminary spectroscopic results from a small-area faint K-excess (KX) survey, and compare KX selection against UVX selection. The aim of the KX method is to produce complete samples of QSOs that are flux-limited in the K band, in order to minimize any selection bias in samples of QSOs from the effects of reddening and extinction. Using the photometric catalogue of the ESO Imaging Survey Chandra Deep Field South (48arcmin^2^) we have identified compact objects with J-K colours redder than the stellar sequence that are brighter than K=19.5. We have obtained spectra of 33 candidates, using the LDSS++ spectrograph on the Anglo-Australian Telescope (AAT). Amongst the 11 bluer candidates, with V-J<3, three are confirmed as QSOs. Identification of the 22 redder candidates with V-J>=3 is substantially incomplete, but so far no reddened QSOs have been found. Near-infrared spectroscopy will be more effective in identifying some of these targets. Only two UVX (U-B<-0.2) sources brighter than K=19.5 are found that are not also KX selected. These are both identified as galactic stars. Thus KX selection appears to select all UVX QSOs. The surface density of QSOs in the blue subsample (V-J<3) at K<=19.5 is 325^+136^_-177_{deg}^-2^. Because identification of the red subsample (V-J>=3) is substantially incomplete, the 2{sigma} upper limit on the density of reddened QSOs is large, <1150{deg}^-2^. As anticipated, at these faint magnitudes the KX sample includes several compact galaxies. Of the 14 with measured redshifts, there are roughly equal numbers of early- and late-type objects. Nearly all the early-type galaxies are found in a single structure at z=0.66.
Lag measurements for 15 z<0.8 QSOs from the SDSS-RM
Short Name:
J/ApJ/818/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
Reverberation mapping (RM) measurements of broad-line region (BLR) lags in z>0.3 quasars are important for directly measuring black hole masses in these distant objects, but so far there have been limited attempts and success given the practical difficulties of RM in this regime. Here we report preliminary results of 15 BLR lag measurements from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project, a dedicated RM program with multi-object spectroscopy designed for RM over a wide redshift range. The lags are based on the 2014 spectroscopic light curves alone (32 epochs over six months) and focus on the H{beta} and Mg II broad lines in the 100 lowest-redshift (z<0.8) quasars included in SDSS-RM; they represent a small subset of the lags that SDSS-RM (including 849 quasars to z~4.5) is expected to deliver. The reported preliminary lag measurements are for intermediate-luminosity quasars at 0.3<~z<0.8, including nine H{beta} lags and six Mg II lags, for the first time extending RM results to this redshift-luminosity regime and providing direct quasar black hole mass estimates over approximately half of cosmic time. The Mg II lags also increase the number of known Mg II lags by several fold and start to explore the utility of Mg II for RM at high redshift. The location of these new lags at higher redshifts on the observed BLR size-luminosity relationship is statistically consistent with previous H{beta} results at z<0.3. However, an independent constraint on the relationship slope at z>0.3 is not yet possible owing to the limitations in our current sample. Our results demonstrate the general feasibility and potential of multi-object RM for z>0.3 quasars.
We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ~135deg^2^ from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ~100 deg^2^ that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.5{deg} of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local Group.
In this work, we report new quasars discovered in fields in the vicinity of the Andromeda (M31) and Triangulum (M33) galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) during the 2013 observational season, the second year of the regular survey. In total, 1330 new quasars are discovered in an area of ~133{deg}^2^ around M31 and M33. With i magnitudes ranging from 14.79 to 20.0 and redshifts from 0.08 to 4.85, the 1330 new quasars represent a significant increase in the number of identified quasars in fields in the vicinity of M31 and M33. Up to now, there have been a total of 1870 quasars discovered by LAMOST in this area. The much enlarged sample of known quasars in this area can potentially be utilized to construct a precise astrometric reference frame for the measurement of minute proper motions of M31, M33 and their associated substructures, which are vital for understanding the formation and evolution of M31, M33 and the Local Group of galaxies. Moreover, in the sample, there are a total of 45, 98 and 225 quasars with i magnitudes brighter than 17.0, 17.5 and 18.0 respectively. In the aforementioned brightness bins, 15, 35 and 84 quasars are reported here for the first time, and 6, 21 and 81 are reported in our previous work. In addition, 0, 1 and 6 are from the Sloan Digital Sky Survey and 24, 41 and 54 are from the NED database. These bright quasars provide an invaluable sample to study the kinematics and chemistry of the interstellar/intergalactic medium of the Local Group.
LAMOST Quasar Survey: quasar properties from DR2&3
Short Name:
J/AJ/155/189
Date:
21 Oct 2021
Publisher:
CDS
Description:
This is the second installment for the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Quasar Survey, which includes quasars observed from 2013 September to 2015 June. There are 9024 confirmed quasars in DR2 and 10911 in DR3. After cross-match with the Sloan Digital Sky Survey (SDSS) quasar catalogs and NED, 12126 quasars are discovered independently. Among them, 2225 quasars were released by SDSS DR12 QSO catalog in 2014 after we finalized the survey candidates. 1801 sources were identified by SDSS DR14 as QSOs. The remaining 8100 quasars are considered as newly founded, and among them, 6887 quasars can be given reliable emission line measurements and the estimated black hole masses. Quasars found in LAMOST are mostly located at low-to-moderate redshifts, with a mean value of 1.5. The highest redshift observed in DR2 and DR3 is 5. We applied emission line measurements to H{alpha}, H{beta}, Mg II, and C IV. We deduced the monochromatic continuum luminosities using photometry data, and estimated the virial black hole masses for the newly discovered quasars. Results are compiled into a quasar catalog, which will be available online.
LAMOST quasar survey: quasar properties from the DR1
Short Name:
J/AJ/151/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present preliminary results of the quasar survey in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes the pilot survey and the first year of the regular survey. There are 3921 quasars reliably identified, among which 1180 are new quasars discovered in the survey. These quasars are at low to median redshifts, with a highest z of 4.83. We compile emission line measurements around the H{alpha}, H{beta}, Mg II, and C IV regions for the new quasars. The continuum luminosities are inferred from SDSS photometric data with model fitting, as the spectra in DR1 are non-flux-calibrated. We also compile the virial black hole mass estimates, with flags indicating the selection methods, and broad absorption line quasars. The catalog and spectra for these quasars are also available. Of the 3921 quasars, 28% are independently selected with optical-infrared colors, indicating that the method is quite promising for the completeness of the quasar survey. LAMOST DR1 and the ongoing quasar survey will provide valuable data for studies of quasars.
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