- ID:
- ivo://CDS.VizieR/J/ApJS/221/7
- Title:
- SDSS QSOs at z<0.8. II. New spectroscopic obs.
- Short Name:
- J/ApJS/221/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic observations that are part of our continuing monitoring campaign of 88 quasars at z<0.7 whose broad H{beta} lines are offset from their systemic redshifts by a few thousand km/s. These quasars have been considered as candidates for hosting supermassive black hole binaries (SBHBs) by analogy with single-lined spectroscopic binary stars. We present the data and describe our improved analysis techniques, which include an extensive evaluation of uncertainties. We also present a variety of measurements from the spectra that are of general interest and will be useful in later stages of our analysis. Additionally, we take this opportunity to study the variability of the optical continuum and integrated flux of the broad H{beta} line. We compare the variability properties of the SBHB candidates to those of a sample of typical quasars with similar redshifts and luminosities observed multiple times during the Sloan Digital Sky Survey. We find that the variability properties of the two samples are similar (variability amplitudes of 10%-30% on timescales of approximately 1-7 years) and that their structure functions can be described by a common model with parameters characteristic of typical quasars. These results suggest that the broad-line regions of SBHB candidates have a similar extent as those of typical quasars. We discuss the implications of this result for the SBHB scenario and the ensuing constraints on the orbital parameters.
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Search Results
- 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/805/96
- Title:
- SDSS-RM project: velocity dispersions of QSOs
- Short Name:
- J/ApJ/805/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present host stellar velocity dispersion measurements for a sample of 88 broad-line quasars at 0.1<z<1 (46 at z>0.6) from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. High signal-to-noise ratio coadded spectra (average S/N~30 per 69km/s pixel) from SDSS-RM allowed for the decomposition of the host and quasar spectra and for measurements of the host stellar velocity dispersions and black hole (BH) masses using the single-epoch (SE) virial method. The large sample size and dynamic range in luminosity (L_5100_=10^43.2-44.7^erg/s) lead to the first clear detection of a correlation between SE virial BH mass and host stellar velocity dispersion far beyond the local universe. However, the observed correlation is significantly flatter than the local relation, suggesting that there are selection biases in high-z luminosity-threshold quasar samples for such studies. Our uniform sample and analysis enable an investigation of the redshift evolution of the M_{dot}_-{sigma}_*_ relation relatively free of caveats by comparing different samples/analyses at disjoint redshifts. We do not observe evolution of the M_{dot}_-{sigma}_*_ relation in our sample up to z~1, but there is an indication that the relation flattens toward higher redshifts. Coupled with the increasing threshold luminosity with redshift in our sample, this again suggests that certain selection biases are at work, and simple simulations demonstrate that a constant M_{dot}_-{sigma}_*_ relation is favored to z~1. Our results highlight the scientific potential of deep coadded spectroscopy from quasar monitoring programs, and offer a new path to probe the co-evolution of BHs and galaxies at earlier times.
- 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/850/140
- Title:
- SDSS spectral analysis of IR-bright DOGs
- Short Name:
- J/ApJ/850/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the ionized gas properties of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme optical/IR color, (i-[22])_AB_>7.0, selected with the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). For 36 IR-bright DOGs that show [OIII]{lambda}5007 emission in the SDSS spectra, we performed a detailed spectral analysis to investigate their ionized gas properties. In particular, we measured the velocity offset (the velocity with respect to the systemic velocity measured from the stellar absorption lines) and the velocity dispersion of the [OIII] line. We found that the derived velocity offset and dispersion of most IR-bright DOGs are larger than those of Seyfert 2 galaxies (Sy2s) at z<0.3, meaning that the IR-bright DOGs show relatively strong outflows compared to Sy2s. This can be explained by the difference in IR luminosity contributed from active galactic nuclei, L_IR_ (AGN), because we found that (i) L_IR_ (AGN) correlates with the velocity offset and dispersion of [OIII] and (ii) our IR-bright DOG sample has larger L_IR_ (AGN) than Sy2s. Nevertheless, the fact that about 75% IR- bright DOGs have a large (>300km/s) velocity dispersion, which is a larger fraction compared to other AGN populations, suggests that IR-bright DOGs are good laboratories to investigate AGN feedback. The velocity offset and dispersion of [OIII] and [NeIII]{lambda}3869 are larger than those of [OII]{lambda}3727, which indicates that the highly ionized gas tends to show stronger outflows.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/183
- Title:
- Segregation effects in DEEP2 galaxy groups
- Short Name:
- J/MNRAS/464/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate segregation phenomena in galaxy groups in the range of 0.2<z<1. We study a sample of groups selected from the 4th Data Release of the DEEP2 galaxy redshift survey. We used only groups with at least eight members within a radius of 4 Mpc. Outliers were removed with the shifting gapper technique and, then, the virial properties were estimated for each group. The sample was divided into two stacked systems: low(z<=0.6) and high (z>0.6) redshift groups. Assuming that the colour index (U-B)_0_ can be used as a proxy for the galaxy type, we found that the fraction of blue (star-forming) objects is higher in the high-z sample, with blue objects being dominant at M_B_>-19.5 for both samples, and red objects being dominant at M_B_<-19.5 only for the low-z sample. Also, the radial variation of the red fraction indicates that there are more red objects with R<R_200_ in the low-z sample than in the high-z sample. Our analysis indicates statistical evidence of kinematic segregation, at the 99 per cent c.l., for the low-z sample: redder and brighter galaxies present lower velocity dispersions than bluer and fainter ones. We also find a weaker evidence for spatial segregation between red and blue objects, at the 70 per cent c.l. The analysis of the high-z sample reveals a different result: red and blue galaxies have velocity dispersion distributions not statistically distinct, although redder objects are more concentrated than the bluer ones at the 95 per cent c.l. From the comparison of blue/red and bright/faint fractions, and considering the approximate lookback time-scale between the two samples (~3Gyr), our results are consistent with a scenario where bright red galaxies had time to reach energy equipartition, while faint blue/red galaxies in the outskirts infall to the inner parts of the groups, thus reducing spatial segregation from z~0.8 to z~0.4.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/9
- Title:
- SFR & gas-phase metallicity in MaNGA gal.
- Short Name:
- J/ApJ/882/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of gas accretion in galaxy evolution is still a matter of debate. The presence of inflows of metal-poor gas that trigger star formation bursts of low metallicity has been proposed as an explanation for the local anticorrelation between star formation rate (SFR) and gas-phase metallicity (Z_g_) found in the literature. In the present study, we show how the anticorrelation is also present as part of a diversified range of behaviors for a sample of more than 700 nearby spiral galaxies from the SDSS-IV MaNGA survey. We have characterized the local relation between SFR and Z_g_ after subtracting the azimuthally averaged radial profiles of both quantities. Of the analyzed galaxies, 60% display an SFR-Z_g_ anticorrelation, with the remaining 40% showing no correlation (19%) or positive correlation (21%). Applying a random forest machine-learning algorithm, we find that the slope of the correlation is mainly determined by the average gas-phase metallicity of the galaxy. Galaxy mass, g-r colors, stellar age, and mass density seem to play a less significant role. This result is supported by the performed second-order polynomial regression analysis. Thus, the local SFR-Z_g_ slope varies with the average metallicity, with the more metal-poor galaxies presenting the lowest slopes (i.e., the strongest SFR-Z_g_ anticorrelations), and reversing the relation for more metal-rich systems. Our results suggest that external gas accretion fuels star formation in metal-poor galaxies, whereas in metal-rich systems, the gas comes from previous star formation episodes.
- ID:
- ivo://CDS.VizieR/J/ApJ/830/14
- Title:
- SIGMA: Keck spectra of z~2 gal. in CANDELS fields
- Short Name:
- J/ApJ/830/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a survey of the internal kinematics of 49 star-forming galaxies at z~2 in the CANDELS fields with the Keck/MOSFIRE spectrograph, Survey in the near-Infrared of Galaxies with Multiple position Angles (SIGMA). Kinematics (rotation velocity V_rot_ and gas velocity dispersion {sigma}_g_) are measured from nebular emission lines which trace the hot ionized gas surrounding star-forming regions. We find that by z~2, massive star-forming galaxies (logM_*_/M_{sun}_>~10.2) have assembled primitive disks: their kinematics are dominated by rotation, they are consistent with a marginally stable disk model, and they form a Tully-Fisher relation. These massive galaxies have values of V_rot_/{sigma}_g_ that are factors of 2-5 lower than local well-ordered galaxies at similar masses. Such results are consistent with findings by other studies. We find that low-mass galaxies (logM_*_/M_{sun}_<~10.2) at this epoch are still in the early stages of disk assembly: their kinematics are often dominated by gas velocity dispersion and they fall from the Tully-Fisher relation to significantly low values of V_rot_. This "kinematic downsizing" implies that the process(es) responsible for disrupting disks at z~2 have a stronger effect and/or are more active in low-mass systems. In conclusion, we find that the period of rapid stellar mass growth at z~2 is coincident with the nascent assembly of low-mass disks and the assembly and settling of high-mass disks.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/48
- Title:
- SLACS. XIII. Galaxy-scale strong lens candidates
- Short Name:
- J/ApJ/851/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the full sample of 118 galaxy-scale strong-lens candidates in the Sloan Lens ACS (SLACS) Survey for the Masses (S4TM) Survey, which are spectroscopically selected from the final data release of the Sloan Digital Sky Survey. Follow-up Hubble Space Telescope (HST) imaging observations confirm that 40 candidates are definite strong lenses with multiple lensed images. The foreground-lens galaxies are found to be early-type galaxies (ETGs) at redshifts 0.06-0.44, and background sources are emission-line galaxies at redshifts 0.22-1.29. As an extension of the SLACS Survey, the S4TM Survey is the first attempt to preferentially search for strong-lens systems with relatively lower lens masses than those in the pre-existing strong-lens samples. By fitting HST data with a singular isothermal ellipsoid model, we find that the total projected mass within the Einstein radius of the S4TM strong-lens sample ranges from 3x10^10^M_{sun}_ to 2x10^11^M_{sun}_. In Shu+ (2015ApJ...803...71S), we have derived the total stellar mass of the S4TM lenses to be 5x10^10^M_{sun}_ to 1x10^12^M_{sun}_. Both the total enclosed mass and stellar mass of the S4TM lenses are on average almost a factor of 2 smaller than those of the SLACS lenses, which also represent the typical mass scales of the current strong-lens samples. The extended mass coverage provided by the S4TM sample can enable a direct test, with the aid of strong lensing, for transitions in scaling relations, kinematic properties, mass structure, and dark-matter content trends of ETGs at intermediate-mass scales as noted in previous studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/327/265
- Title:
- SMAC. III. Fundamental Plane catalog
- Short Name:
- J/MNRAS/327/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the construction of a new, standardized all-sky catalogue of Fundamental Plane (FP) data from early-type galaxies in clusters, for peculiar velocity applications. This catalogue is based on a compilation of spectroscopic and photometric data consisting of data reported in previous papers of this series, plus data from published sources.
