Quasar accretion-disc outflows might play an important role in galaxy evolution, but they are notoriously difficult to study due to line saturation and blending problems in the Ly α forest. We ...circumvent these problems by constructing median composite spectra of diverse broad absorption lines (BALs) and `mini-BALs' in SDSS-III BOSS quasars at redshifts 2.3 ≤ z ≤ 3.5. Sorting by C IV λλ1549,1551 absorption-line strength with Al III λλ1855,1863 as an additional indicator of low ionizations (LoBALs) we find the following: (1) Deeper and broader BALs are accompanied by weaker He II λ1640 emission lines, consistent with softer ionizing spectra producing more effective radiative acceleration. (2) P V λλ1118,1128 absorption is present with resolved ∼1:1 depth ratios in all composites from mini-BALs to strong BALs indicating that line saturation, large total column densities log NH(cm-2) ≳ 22.7, and large ionization parameters log U ≳ -0.5 are common. (3) Different observed depths in saturated lines identify inhomogeneous partial covering on spatial scales ≲0.006 pc, where weak/low-abundance transitions like P V form in small high-column density clumps while stronger/broader lines like C IV form in larger regions. (4) Excited-state S IV* λ1073 and C III* λ1176 lines in BAL outflows indicate typical densities ne ≳ 3 × 105 cm-3 and maximum radial distances R ≲ 23 pc from the quasars. (5) For reasonable actual distances, the median BAL outflow has minimum kinetic energy LK/L ≳ 0.005(R/1.2 pc) sufficient for feedback to galaxy evolution. (6) LoBAL quasars have the largest median outflow column densities, highest velocities, and weakest He II λ1640 emission in our study; they appear to be at one extreme in a distribution of quasar properties where softer ionizing spectra drive more powerful outflows.
We develop a new method, which is based on the optimal redshift weighting scheme, to extract the maximal tomographic information of baryonic acoustic oscillations (BAO) and redshift space distortions ...(RSD) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 14 quasar (DR14Q) survey. We validate our method using the Extended Zel’dovich mocks, and apply our pipeline to the eBOSS DR14Q sample in the redshift range of 0.8 < |$z$| < 2.2. We report a joint measurement of fσ_8 and two-dimensional BAO parameters D_A and H at four effective redshifts of |$z$|_eff = 0.98, 1.23, 1.52, and 1.94, and provide the full data covariance matrix. Using our measurement combined with BOSS DR12, Main Galaxy Sample (MGS), and 6 degree Field Galaxy Survey (6dFGS) BAO measurements, we find that the existence of dark energy is supported by observations at a 7.4σ significance level. Combining our measurement with BOSS DR12 and Planck observations, we constrain the gravitational growth index to be γ = 0.580 ± 0.082, which is fully consistent with the prediction of general relativity. This paper is part of a set that analyses the eBOSS DR14 quasar sample.
We analyse the clustering of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar sample (DR14Q). We measure the redshift space distortions using ...the power-spectrum monopole, quadrupole, and hexadecapole inferred from 148 659 quasars between redshifts 0.8 and 2.2, covering a total sky footprint of 2112.9 deg^2. We constrain the logarithmic growth of structure times the amplitude of dark matter density fluctuations, fσ_8, and the Alcock–Paczynski dilation scales that allow constraints to be placed on the angular diameter distance (z) and the Hubble H(z) parameter. At the effective redshift of z_eff = 1.52, fσ_8(z_eff) = 0.420 ± 0.076, $$H(z_{\rm eff})=162\pm 12\, (r_s^{\rm fid}/r_s)\,{\rm km\, s}^{-1}\,{\rm Mpc}^{-1}$$, and $$D_A(z_{\rm eff})=1.85\pm 0.11\times 10^3\,(r_s/r_s^{\rm fid})\,{\rm Mpc}$$, where r_s is the comoving sound horizon at the baryon drag epoch and the superscript ‘fid’ stands for its fiducial value. The errors take into account the full error budget, including systematics and statistical contributions. These results are in full agreement with the current Λ-Cold Dark Matter cosmological model inferred from Planck measurements. Finally, we compare our measurements with other eBOSS companion papers and find excellent agreement, demonstrating the consistency and complementarity of the different methods used for analysing the data.
ABSTRACT As part of the Sloan Digital Sky Survey (SDSS) IV the extended Baryon Oscillation Spectroscopic Survey (eBOSS) will improve measurements of the cosmological distance scale by applying the ...Baryon Acoustic Oscillation (BAO) method to quasar samples. eBOSS will adopt two approaches to target quasars over 7500 deg2. First, a "CORE" quasar sample will combine the optical selection in ugriz using a likelihood-based routine called XDQSOz, with a mid-IR-optical color cut. eBOSS CORE selection (to g < 22 or r < 22) should return ∼70 deg−2 quasars at redshifts 0.9 < z < 2.2 and ∼7 deg−2z > 2.1 quasars. Second, a selection based on variability in multi-epoch imaging from the Palomar Transient Factory should recover an additional ∼3-4 deg−2z > 2.1 quasars to g < 22.5. A linear model of how imaging systematics affect target density recovers the angular distribution of eBOSS CORE quasars over 96.7% (76.7%) of the SDSS north (south) Galactic Cap area. The eBOSS CORE quasar sample should thus be sufficiently dense and homogeneous over 0.9 < z < 2.2 to yield the first few-percent-level BAO constraint near eBOSS quasars at z > 2.1 will be used to improve BAO measurements in the Ly Forest. Beyond its key cosmological goals, eBOSS should be the next-generation quasar survey, comprising >500,000 new quasars and >500,000 uniformly selected spectroscopically confirmed 0.9 < z < 2.2 quasars. At the conclusion of eBOSS, the SDSS will have provided unique spectra for more than 800,000 quasars.
We present the final Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog from Data Release 16 of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). This catalog comprises the largest ...selection of spectroscopically confirmed quasars to date. The full catalog includes two subcatalogs (the current versions are DR16Q_v4 and DR16Q_Superset_v3 at https://data.sdss.org/sas/dr16/eboss/qso/DR16Q/): a "superset" of all SDSS-IV/eBOSS objects targeted as quasars containing 1,440,615 observations and a quasar-only catalog containing 750,414 quasars, including 225,082 new quasars appearing in an SDSS data release for the first time, as well as known quasars from SDSS-I/II/III. We present automated identification and redshift information for these quasars alongside data from visual inspections for 320,161 spectra. The quasar-only catalog is estimated to be 99.8% complete with 0.3%-1.3% contamination. Automated and visual inspection redshifts are supplemented by redshifts derived via principal component analysis and emission lines. We include emission-line redshifts for H , Hβ, Mg ii, C iii, C iv, and Ly . Identification and key characteristics generated by automated algorithms are presented for 99,856 broad absorption-line quasars and 35,686 damped Lyman alpha quasars. In addition to SDSS photometric data, we also present multiwavelength data for quasars from the Galaxy Evolution Explorer, UKIDSS, the Wide-field Infrared Survey Explorer, FIRST, ROSAT/2RXS, XMM-Newton, and Gaia. Calibrated digital optical spectra for these quasars can be obtained from the SDSS Science Archive Server.
We describe the automated spectral classification, redshift determination, and parameter measurement pipeline in use for the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky ...Survey UI (SDSS-III) as of the survey's ninth data release (DR9), encompassing 831,000 moderate-resolution optical spectra. We give a review of the algorithms employed, and describe the changes to the pipeline that have been implemented for BOSS relative to previous SDSS-I/II versions, including new sets of stellar, galaxy, and quasar redshift templates. We test the accuracy of these statistical redshift error estimates using repeat observations, finding them underestimated by a factor of 1.19-1.34 for galaxies and by a factor of two for quasars. We assess the impact of sky-subtraction quality, signal-to-noise ratio, and other factors on galaxy redshift success. Finally, we document known issues with the BOSS DR9 spectroscopic data set and describe directions of ongoing development
The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year spectroscopic survey of 10,000 deg2, achieved first light in late 2009. One of the key goals of BOSS is to measure the ...signature of baryon acoustic oscillations (BAOs) in the distribution of Lyα absorption from the spectra of a sample of ~150,000 z > 2.2 quasars. Along with measuring the angular diameter distance at z ≈ 2.5, BOSS will provide the first direct measurement of the expansion rate of the universe at z > 2. One of the biggest challenges in achieving this goal is an efficient target selection algorithm for quasars in the redshift range 2.2 < z < 3.5, where their colors tend to overlap those of the far more numerous stars. During the first year of the BOSS survey, quasar target selection (QTS) methods were developed and tested to meet the requirement of delivering at least 15 quasars deg-2 in this redshift range, with a goal of 20 out of 40 targets deg-2 allocated to the quasar survey. To achieve these surface densities, the magnitude limit of the quasar targets was set at g <= 22.0 or r <= 21.85. While detection of the BAO signature in the distribution of Lyα absorption in quasar spectra does not require a uniform target selection algorithm, many other astrophysical studies do. We have therefore defined a uniformly selected subsample of 20 targets deg-2, for which the selection efficiency is just over 50% (~10 z > 2.20 quasars deg-2). This "CORE" subsample will be fixed for Years Two through Five of the survey. For the remaining 20 targets deg-2, we will continue to develop improved selection techniques, including the use of additional data sets beyond the Sloan Digital Sky Survey (SDSS) imaging data. In this paper, we describe the evolution and implementation of the BOSS QTS algorithms during the first two years of BOSS operations (through 2011 July), in support of the science investigations based on these data, and we analyze the spectra obtained during the first year. During this year, 11,263 new z > 2.20 quasars were spectroscopically confirmed by BOSS, roughly double the number of previously known quasars with z > 2.20. Our current algorithms select an average of 15 z > 2.20 quasars deg-2 from 40 targets deg-2 using single-epoch SDSS imaging. Multi-epoch optical data and data at other wavelengths can further improve the efficiency and completeness of BOSS QTS.
We measure the two-point clustering of spectroscopically confirmed quasars from the final sample of the Baryon Oscillation Spectroscopic Survey (BOSS) on comoving scales of 4 ≲ s ≲ 22 h
−1 Mpc. The ...sample covers 6950 deg2 ∼ 19 (h
− 1Gpc)3 and, over the redshift range 2.2 ≤ z ≤ 2.8, contains 55 826 homogeneously selected quasars, which is twice as many as in any similar work. We deduce b
Q = 3.54 ± 0.10; the most precise measurement of quasar bias to date at these redshifts. This corresponds to a host halo mass of ∼2 × 1012 h
−1 M⊙ with an implied quasar duty cycle of ∼1 per cent. The real-space projected correlation function is well fitted by a power law of index 2 and correlation length r
0 = (8.12 ± 0.22) h
− 1 Mpc over scales of 4 ≲ r
p ≲ 25 h
−1 Mpc. To better study the evolution of quasar clustering at moderate redshift, we extend the redshift range of our study to z ∼ 3.4 and measure the bias and correlation length of three subsamples over 2.2 ≤ z ≤ 3.4. We find no significant evolution of r
0 or bias over this range, implying that the host halo mass of quasars decreases somewhat with increasing redshift. We find quasar clustering remains similar over a decade in luminosity, contradicting a scenario in which quasar luminosity is monotonically related to halo mass at z ≈ 2.5. Our results are broadly consistent with previous BOSS measurements, but they yield more precise constraints based upon a larger and more uniform data set.
We have used flux-transmission correlations in Lyα forests to measure the imprint of baryon acoustic oscillations (BAO). The study uses spectra of 157 783 quasars in the redshift range 2.1 ≤ z ≤ 3.5 ...from the Sloan Digital Sky Survey (SDSS) data release 12 (DR12). Besides the statistical improvements on our previous studies using SDSS DR9 and DR11, we have implemented numerous improvements in the analysis procedure, allowing us to construct a physical model of the correlation function and to investigate potential systematic errors in the determination of the BAO peak position. The Hubble distance, DH = c/H(z), relative to the sound horizon is DH(z = 2.33) /rd = 9.07 ± 0.31. The best-determined combination of comoving angular-diameter distance, DM, and the Hubble distance is found to be DH0.7DM0.3 /rd = 13.94 ± 0.35. This value is 1.028 ± 0.026 times the prediction of the flat-ΛCDM model consistent with the cosmic microwave background (CMB) anisotropy spectrum. The errors include marginalization over the effects of unidentified high-density absorption systems and fluctuations in ultraviolet ionizing radiation. Independently of the CMB measurements, the combination of our results and other BAO observations determine the open-ΛCDM density parameters to be ΩM = 0.296 ± 0.029, ΩΛ = 0.699 ± 0.100 and Ωk = −0.002 ± 0.119.
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Spectropolarimetry is a powerful technique that has provided critical support for the geometric unification model of local active galactic nuclei. In this paper, we present optical rest-frame ...ultraviolet (UV) Keck spectropolarimetry of five luminous obscured (type 2) and extremely red quasars (ERQs) at z ≃ 2.5. Three objects reach polarization fractions of ≳10 per cent in the continuum. We prefer dust scattering as the dominant scattering and polarization mechanism in our targets, though electron scattering cannot be completely excluded. Emission lines are polarized at a lower level than the continuum. This suggests that the emission-line region exists on similar spatial scales as the scattering region. In three objects, we detect an intriguing 90°swing in the polarization position angle as a function of line-of-sight velocity in the emission lines of Ly α, C IV, and N V. We interpret this phenomenon in the framework of a geometric model with an equatorial scattering region in which the scattering material is outflowing at several thousand km s-1. Our model explains several salient features of observations by scattering on scales of a few tens of pc. Our observations provide a tantalizing view of the inner region geometry and kinematics of high-redshift obscured and ERQs. Our data and modelling lend strong support for toroidal obscuration and powerful outflows on the scales of the UV emission line region, in addition to the larger scale outflows inferred previously from the optical emission line kinematics.
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