We present a survey of the C ii 158 m line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 quasars using the Atacama Large Millimeter Array (ALMA) at resolution. The C ii ...line was significantly detected (at - ) in 23 sources (85%). We find typical line luminosities of , and an average line width of ∼385 . The C ii-to-far-infrared luminosity ratios (C ii/FIR) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. Four quasar host galaxies are clearly resolved in their C ii emission on a few kpc scales. Basic estimates of the dynamical masses of the host galaxies give masses between 2 × 1010 and 2 × 1011 , i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes ( , assuming Eddington-limited accretion). In stacked ALMA C ii spectra of individual sources in our sample, we find no evidence of a deviation from a single Gaussian profile. The quasar luminosity does not strongly correlate with either the C ii luminosity or equivalent width. This survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of ALMA at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe.
We present deep near-infrared spectroscopy of six quasars at 6.1 ≤ z ≤ 6.7 with Very Large Telescope/X-Shooter and Gemini-N/GNIRS. Our objects, originally discovered through a wide-field optical ...survey with the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP), have the lowest luminosities (−25.5 mag ≤ M1450 ≤ −23.1 mag) of the z > 5.8 quasars with measured black hole (BH) masses. From single-epoch mass measurements based on Mg ii λ2798, we find a wide range in BH masses, from MBH = 107.6 to 109.3 M . The Eddington ratios Lbol/LEdd range from 0.16 to 1.1, but the majority of the HSC quasars are powered by MBH ∼ 109 M supermassive black holes (SMBHs) accreting at sub-Eddington rates. The Eddington ratio distribution of the HSC quasars is inclined to lower accretion rates than those of Willott et al., who measured the BH masses for similarly faint z ∼ 6 quasars. This suggests that the global Eddington ratio distribution is wider than has previously been thought. The presence of MBH ∼ 109 M SMBHs at z ∼ 6 cannot be explained with constant sub-Eddington accretion from stellar remnant seed BHs. Therefore, we may be witnessing the first buildup of the most massive BHs in the first billion years of the universe, the accretion activity of which is transforming from active growth to a quiescent phase. Measurements of a larger complete sample of z 6 low-luminosity quasars, as well as deeper observations with future facilities, will enable us to better understand the early SMBH growth in the reionization epoch.
ABSTRACT We present the discovery of nine quasars at identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of quasars in the SDSS footprint. Our final sample ...consists of 52 quasars at , including 29 quasars with mag selected from 11,240 deg2 of the SDSS single-epoch imaging survey (the main survey), 10 quasars with selected from 4223 deg2 of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to mag from the 277 deg2 in Stripe 82. They span a wide luminosity range of . This well-defined sample is used to derive the quasar luminosity function (QLF) at . After combining our SDSS sample with two faint ( mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope β of the QLF is well constrained to be . Due to the small number of low-luminosity quasars, the faint-end slope and the characteristic magnitude are less well constrained, with and mag. The spatial density of luminous quasars, parametrized as , drops rapidly from to 6, with . Based on our fitted QLF and assuming an intergalactic medium (IGM) clumping factor of C = 3, we find that the observed quasar population cannot provide enough photons to ionize the IGM at ∼90% confidence. Quasars may still provide a significant fraction of the required photons, although much larger samples of faint quasars are needed for more stringent constraints on the quasar contribution to reionization.
We report initial results from a large Gemini program to observe z 5.7 quasars with GNIRS near-IR spectroscopy. Our sample includes 50 quasars with simultaneous ∼0.85-2.5 m spectra covering the ...rest-frame ultraviolet and major broad emission lines from Ly to Mg ii. We present spectral measurements for these quasars and compare with their lower redshift counterparts at z = 1.5-2.3. We find that when quasar luminosity is matched, there are no significant differences between the rest-UV spectra of z 5.7 quasars and the low-z comparison sample. High-z quasars have similar continuum and emission line properties and occupy the same region in the black hole mass and luminosity space as the comparison sample, accreting at an average Eddington ratio of ∼0.3. There is no evidence for super-Eddington accretion or hypermassive (>1010 M ) black holes within our sample. We find a mild excess of quasars with weak C iv lines relative to the control sample. Our results, corroborating earlier studies but with better statistics, demonstrate that these high-z quasars are already mature systems of accreting supermassive black holes operating with the same physical mechanisms as those at lower redshifts.
Abstract
The relationship between quasars and their host galaxies provides clues on how supermassive black holes (SMBHs) and massive galaxies are jointly assembled. To elucidate this connection, we ...measure the structural and photometric properties of the host galaxies of ∼5000 Sloan Digital Sky Survey quasars at 0.2 <
z
< 1 using five-band (
grizy
) optical imaging from the Hyper Suprime-Cam Subaru Strategic Program. An automated analysis tool is used to forward-model the blended emission of the quasar as characterized by the point-spread function and the underlying host galaxy as a two-dimensional Sérsic profile. We find that quasars are preferentially hosted by massive star-forming galaxies with disklike light profiles. Furthermore, the size distribution of quasar hosts is broad at a given stellar mass and the average values exhibit a size–stellar mass relation as seen with inactive galaxies. In contrast, the sizes of quasar hosts are more compact than those of inactive star-forming galaxies on average, but not as compact as those of quiescent galaxies of similar stellar masses. This is true irrespective of quasar properties, including the bolometric luminosity, Eddington ratio, and black hole mass. These results are consistent with a scenario in which galaxies are concurrently fueling an SMBH and building their stellar bulge from a centrally concentrated gas reservoir. Alternatively, quasar hosts may be experiencing a compaction process in which stars from the disk and inflowing gas are responsible for growing the bulge. In addition, we confirm that the host galaxies of type 1 quasars have a bias of being closer to face-on systems, suggesting that galactic-scale dust can contribute to obscuring the broad-line region.
The physics and demographics of type 2 quasars remain poorly understood, and new samples of such objects selected in a variety of ways can give insight into their physical properties, evolution, and ...relationship to their host galaxies. We present a sample of 2758 type 2 quasars at z ≲ 1 from the Sloan Digital Sky Survey-III (SDSS-III)/Baryon Oscillation Spectroscopic Survey (BOSS) spectroscopic data base, selected on the basis of their emission-line properties. We probe the luminous end of the population by requiring the rest-frame equivalent width of O iii to be >100 Å. We distinguish our objects from star-forming galaxies and type 1 quasars using line widths, standard emission line ratio diagnostic diagrams at z < 0.52 and detection of Ne vλ3426 Å at z > 0.52. The majority of our objects have O iii luminosities in the range 1.2 × 1042–3.8 × 1043 erg s−1 and redshifts between 0.4 and 0.65. Our sample includes over 400 type 2 quasars with incorrectly measured redshifts in the BOSS data base; such objects often show kinematic substructure or outflows in the O iii line. The majority of the sample has counterparts in the Wide-field Infrared Survey Explorer survey, with median infrared luminosity νL
ν12 μm = 4.2 × 1044 erg s− 1. Only 34 per cent of the newly identified type 2 quasars would be selected by infrared colour cuts designed to identify obscured active nuclei, highlighting the difficulty of identifying complete samples of type 2 quasars. We make public the multi-Gaussian decompositions of all O iii profiles for the new sample and for 568 type 2 quasars from SDSS I/II, together with non-parametric measures of the O iii line profile shapes. We also identify over 600 candidate double-peaked O iii profiles.
We present Karl G. Jansky Very Large Array observations of the CO (2−1) line emission toward three far-infrared luminous quasars at z ∼ 6: SDSS J231038.88+185519.7 and SDSS J012958.51−003539.7 with ...∼0 6 resolution and SDSS J205406.42−000514.8 with ∼2 1 resolution. All three sources are detected in the CO (2−1) line emission-one source is marginally resolved, and the other two appear as point sources. Measurements of the CO (2−1) line emission allow us to calculate the molecular gas mass even without a CO excitation model. The inferred molecular gas masses are (0.8-4.3) × 1010 M . The widths and redshifts derived from the CO (2−1) line are consistent with previous CO (6−5) and C ii measurements. We also report continuum measurements using Herschel for SDSS J231038.88+185519.7 and SDSS J012958.51−003539.7, and for SDSS J231038.88+185519.7 data obtained at ∼140 and ∼300 GHz using the Atacama Large Millimeter/submillimeter Array. In the case of SDSS J231038.88+185519.7, we present a detailed analysis of the spectral energy distribution and derive the dust temperature (∼40 K), the dust mass (∼109 M ), the far-infrared luminosity (8-1000 m; ∼1013 L ), and the star formation rate (2400-2700 M yr−1). Finally, an analysis of the photodissociation regions associated with the three high-redshift quasars indicates that the interstellar medium in these sources has similar properties to local starburst galaxies.
Abstract
We present and characterize the catalog of galaxy shape measurements that will be used for cosmological weak lensing measurements in the Wide layer of the first year of the Hyper Suprime-Cam ...(HSC) survey. The catalog covers an area of 136.9 deg2 split into six fields, with a mean i-band seeing of 0${^{\prime\prime}_{.}}$58 and 5σ point-source depth of i ∼ 26. Given conservative galaxy selection criteria for first-year science, the depth and excellent image quality results in unweighted and weighted source number densities of 24.6 and 21.8 arcmin−2, respectively. We define the requirements for cosmological weak lensing science with this catalog, then focus on characterizing potential systematics in the catalog using a series of internal null tests for problems with point-spread function (PSF) modeling, shear estimation, and other aspects of the image processing. We find that the PSF models narrowly meet requirements for weak lensing science with this catalog, with fractional PSF model size residuals of approximately 0.003 (requirement: 0.004) and the PSF model shape correlation function ρ1 < 3 × 10−7 (requirement: 4 × 10−7) at 0${^{\circ}_{.}}$5 scales. A variety of galaxy shape-related null tests are statistically consistent with zero, but star–galaxy shape correlations reveal additive systematics on >1° scales that are sufficiently large as to require mitigation in cosmic shear measurements. Finally, we discuss the dominant systematics and the planned algorithmic changes to reduce them in future data reductions.
We determine the underlying shapes of spiral and elliptical galaxies in the Sloan Digital Sky Survey Data Release 6 (SDSS DR6) from the observed distribution of projected galaxy shapes, taking into ...account the effects of dust extinction and reddening. We assume that the underlying shapes of spirals and ellipticals are well approximated by triaxial ellipsoids. The elliptical galaxy data are consistent with oblate spheroids, with a correlation between luminosity and ellipticity: the mean values of minor to middle axis ratios are 0.41 ± 0.03 for Mr≈−18 ellipticals and 0.76 ± 0.04 for Mr≈−22.5 ellipticals. Ellipticals show almost no dependence of axial ratio on galaxy colour, implying a negligible dust optical depth. There is a strong variation of spiral galaxy shapes with colour indicating the presence of dust. The intrinsic shapes of spiral galaxies in the SDSS DR6 are consistent with flat discs with a mean and dispersion of thickness to diameter ratio of (21 ± 2) per cent, and a face-on ellipticity, e, of ln(e) =−2.33 ± 0.79. Not including the effects of dust in the model leads to discs that are systematically rounder by up to 60 per cent. More luminous spiral galaxies tend to have thicker and rounder discs than lower luminosity spirals. Both elliptical and spiral galaxies tend to be rounder for larger galaxies. The marginalized value of the edge-on r-band dust extinction E0 in spiral galaxies is E0≃ 0.45 mag for galaxies of median colours, increasing to E0= 1 mag for g−r > 0.9 and E0= 1.9 for the luminous and most compact galaxies, with half-light radii <2 h−1 kpc.
A Study of Two Diffuse Dwarf Galaxies in the Field Greco, Johnny P.; Goulding, Andy D.; Greene, Jenny E. ...
Astrophysical journal/The Astrophysical journal,
10/2018, Letnik:
866, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present optical long-slit spectroscopy and far-ultraviolet to mid-infrared spectral energy distribution fitting of two diffuse dwarf galaxies, LSBG-285 and LSBG-750, which were recently discovered ...by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We measure redshifts using H line emission and find that these galaxies are at comoving distances of 25 and 41 Mpc, respectively, after correcting for the local velocity field. They have effective radii of reff = 1.2 and 1.8 kpc and stellar masses of M (2-3) × 107 M . There are no massive galaxies ( ) within a comoving separation of at least 1.5 Mpc from LSBG-285 and 2 Mpc from LSBG-750. These sources are similar in size and surface brightness to ultradiffuse galaxies, except they are isolated, star-forming objects that were optically selected in an environmentally blind survey. Both galaxies likely have low stellar metallicities Z /Z < −1.0 and are consistent with the stellar mass-metallicity relation for dwarf galaxies. We set an upper limit on LSBG-750's rotational velocity of ∼50 km s−1, which is comparable to dwarf galaxies of similar stellar mass with estimated halo masses <1011 M . We find tentative evidence that the gas-phase metallicities in both of these diffuse systems are high for their stellar mass, though a statistically complete, optically selected galaxy sample at very low surface brightness will be necessary to place these results into context with the higher surface brightness galaxy population.
![An ALMA [C ii] Survey of 27...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "An ALMA [C ii] Survey of 27 Quasars at z > 5.94")
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