- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/323
- Title:
- SDSS quasars with PV broad absorption
- Short Name:
- J/MNRAS/469/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor in feedback to galaxy evolution. Understanding the nature of these flows requires further constraints on their physical properties, including their column densities, for which well-studied BALs, such as CIV {lambda}{lambda}1548,1551, typically provide only a lower limit because of saturation effects. Low-abundance lines, such as PV {lambda}{lambda}1118,1128, indicate large column densities, implying that outflows more powerful than measurements of CIV alone would indicate. We search through a sample of 2694 BAL quasars from the Sloan Digital Sky Survey III/Baryon Oscillation Spectroscopic Survey data release 9 quasar catalogue for such absorption, and we identify 81 'definite' and 86 'probable' detections of PV broad absorption, yielding a firm lower limit of 3.0-6.2 per cent for the incidence of such absorption among BAL quasars. The PV-detected quasars tend to have stronger CIV and SiIV absorption, as well as a higher incidence of LoBAL absorption, than the overall BAL quasar population. Many of the PV-detected quasars have CIV troughs that do not reach zero intensity (at velocities where PV is detected), confirming that the outflow gas only partially covers the UV continuum source. P V appears significantly in a composite spectrum of non-PV-detected BAL quasars, indicating that P V absorption (and large column densities) is much more common than indicated by our search results. Our sample of PV detections significantly increases the number of known PV detections, providing opportunities for follow-up studies to better understand BAL outflow energetics.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/21
- Title:
- SDSS RM project: <10day CIV BAL variability
- Short Name:
- J/ApJ/872/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We systematically investigate short-timescale (<10 day rest-frame) CIV broad absorption-line (BAL) variability to constrain quasar-wind properties and provide insights into BAL-variability mechanisms in quasars. We employ data taken by the Sloan Digital Sky Survey Reverberation Mapping project, as the rapid cadence of these observations provides a novel opportunity to probe BAL variability on shorter rest-frame timescales than have previously been explored. In a sample of 27 quasars with a median of 58 spectral epochs per quasar, we have identified 15 quasars (55_-14_^+18^%), 19 of 37 CIV BAL troughs (51_-12_^+15^%), and 54 of 1460 epoch pairs (3.7%+/-0.5%) that exhibit significant CIV BAL equivalent-width variability on timescales of less than 10 days in the quasar rest frame. These frequencies indicate that such variability is common among quasars and BALs, though somewhat rare among epoch pairs. Thus, models describing BALs and their behavior must account for variability on timescales down to less than a day in the quasar rest frame. We also examine a variety of spectral characteristics and find that, in some cases, BAL variability is best described by ionization-state changes, while other cases are more consistent with changes in covering fraction or column density. We adopt a simple model to constrain the density and radial distance of two outflows appearing to vary by ionization-state changes, yielding outflow density lower limits consistent with previous work.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/1
- Title:
- SDSS-Spitzer AGN properties
- Short Name:
- J/ApJ/758/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from the Sloan Digital Sky Survey (SDSS) and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic contributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [Ne II] 12.8{mu}m emission line is well correlated with the star formation rate measured from the SDSS spectra, and this holds for the star-forming, composite, and AGN-dominated systems. AGNs show a clear excess of [Ne III] 15.6{mu}m emission relative to star-forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including the mid-IR spectral slope, the ratio of the [Ne V] 14.3{mu}m to [Ne II] 12.8{mu}m fluxes, the equivalent widths of the 7.7{mu}m, 11.3{mu}m, and 17{mu}m polycyclic aromatic hydrocarbon (PAH) features, and the optical "D" parameter which measures the distance at which a source lies from the locus of star-forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN dominance. We find that the PAH 11.3{mu}m feature is significantly suppressed in the most AGN-dominated systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/126
- Title:
- SEAMBHs. V. The third year
- Short Name:
- J/ApJ/825/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports results of the third-year campaign of monitoring super-Eddington accreting massive black holes (SEAMBHs) in active galactic nuclei (AGNs) between 2014 and 2015. Ten new targets were selected from the quasar sample of the Sloan Digital Sky Survey (SDSS), which have generally been more luminous than the SEAMBH candidates in the last two years. H{beta} lags ({tau}_H{beta}_) in five of the 10 quasars have been successfully measured in this monitoring season. We find that the lags are generally shorter, by large factors, than those of objects with same optical luminosity, in light of the well-known R_H{beta}_-L_5100_ relation. The five quasars have dimensionless accretion rates of dM/dt=10-10^3^. Combining these with measurements of the previous SEAMBHs, we find that the reduction of H{beta} lags depends tightly on accretion rates, {tau}_H{beta}_/{tau}_R-L_{propto}(dM/dt)^-0.42^, where {tau}_R-L_ is the H{beta} lag from the normal R_H{beta}_-L_5100_ relation. Fitting 63 mapped AGNs, we present a new scaling relation for the broad-line region: R_H{beta}_={alpha}_1_l_44_^{beta}1^min [1,(dM/dt)/(dM/dt)_c_)^-{gamma}1^], where l_44_=L_5100_/10^44^erg/s is the 5100{AA} continuum luminosity, and the coefficients are {alpha}_1_=29.6_-2.8_^+2.7^ lt-day, {beta}1=0.56_-0.03_^+0.03^, {gamma}1=0.52_-0.16_^+0.33^, and (dM/dt)_c_=11.19_-6.22_^+2.29^. This relation is applicable to AGNs over a wide range of accretion rates, from 10^-3^ to 10^3^. Implications of this new relation are briefly discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/460/695
- Title:
- Search for Associations Containing Young stars
- Short Name:
- J/A+A/460/695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from a high-resolution optical spectroscopic survey aimed to search for nearby young associations and young stars among optical counterparts of ROSAT All-Sky Survey (<IX/10> and <IX/29>, X-ray sources in the Southern Hemisphere. We selected 1953 late-type (B-V>=0.6), potentially young, optical counterparts out of a total of 9574 1RXS sources for follow-up observations. At least one high-resolution spectrum was obtained for each of 1511 targets. This paper is the first in a series presenting the results of the SACY survey. Here we describe our sample and our observations. We describe a convergence method in the (UVW) velocity space to find associations. As an example, we discuss the validity of this method in the framework of the Beta Pic Association.
- ID:
- ivo://CDS.VizieR/J/ApJ/738/69
- Title:
- SEDs of galaxies at 3.8<z<5 in GOODS
- Short Name:
- J/ApJ/738/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present evidence for strong H{alpha} emission in galaxies with spectroscopic redshifts in the range of 3.8<z<5.0 over the Great Observatories Origins Deep Survey fields. Among 74 galaxies detected in the Spitzer IRAC 3.6 and 4.5um bands, more than 70% of the galaxies show clear excess at 3.6um compared to the expected flux density from stellar continuum only. We provide evidence that this 3.6um excess is due to H{alpha} emission redshifted into the 3.6um band, and classify these 3.6um excess galaxies to be H{alpha} emitter (HAE) candidates. The selection of HAE candidates using an excess in broadband filters is sensitive to objects whose rest-frame H{alpha} equivalent width (EW) is larger than 350{AA}. The H{alpha} inferred star formation rates (SFRs) of the HAEs range between 20 and 500M_{sun}_/yr and are a factor of ~6 larger than SFRs inferred from the UV continuum. The ratio between the H{alpha} luminosity and UV luminosity of HAEs is also on average larger than that of local starbursts.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1398
- Title:
- SFR for starburst galaxies
- Short Name:
- J/ApJ/701/1398
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparison of star formation rates (SFR) determined from mid-infrared 7.7um polycyclic aromatic hydrocarbon (PAH) luminosity [SFR(PAH)], from 1.4GHz radio luminosity [SFR(radio)], and from far-ultraviolet luminosity [SFR(UV)] for a sample of 287 starburst galaxies with z<0.5 having Spitzer IRS observations.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A135
- Title:
- Sgr dSph CEMP-r/s star abundance analysis
- Short Name:
- J/A+A/641/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery and chemical abundance analysis of the first CEMP-r/s star detected in the Sagittarius dwarf spheroidal galaxy (Sgr dSph) by means of UVES high-resolution spectra. The star, found in the outskirts of Sgr dSph, along the major axis of the main body, is a moderately metal-poor giant (Teff=4753K, logg=1.75, [Fe/H]=-1.55) with [C/Fe]=1.13, placing it in the so-called "high-carbon band", and strong s-process and r-process enrichment ([Ba/Fe]=1.4, [Eu/Fe]=1.01). Abundances of 29 elements from C to Dy were obtained. The chemical pattern appears to be best fitted by a scenario where an r-process pollution event pre-enriched the material out of which the star was born as secondary in a binary system whose primary evolved through the AGB phase, providing C- and s-process enrichment.
- ID:
- ivo://CDS.VizieR/J/ApJS/220/20
- Title:
- Si and Ca high-velocity features in SNe Ia
- Short Name:
- J/ApJS/220/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high-velocity features (HVFs) in optical spectra of type Ia supernovae (SNe Ia) are examined with a large sample including very early-time spectra (e.g., t<-7days). Multiple Gaussian fits are applied to examine the HVFs and their evolutions, using constraints on expansion velocities for the same species (i.e., SiII5972 and SiII6355). We find that strong HVFs tend to appear in SNe Ia with smaller decline rates (e.g., {Delta}m_15_(B)<~1.4mag), clarifying that the finding by Childress et al. (2014MNRAS.437..338C) for the Ca-HVFs in near-maximum-light spectra applies both to the Si-HVFs and Ca-HVFs in the earlier phase. The Si-HVFs seem to be more common in rapidly expanding SNe Ia, which is different from the earlier result that Ca-HVFs are associated with SNe Ia that have slower SiII6355 velocities at maximum light (i.e., V^Si^_max_). Moreover, SNe Ia with both stronger HVFs at early phases and larger V^Si^_max_ are found to have noticeably redder B-V colors and to occur preferentially in the inner regions of their host galaxies, while those with stronger HVFs but smaller V^Si^_max_ show opposite tendencies, suggesting that these two subclasses have different explosion environments and their HVFs may have different origins. We further examine the relationships between the absorption features of SiII6355 and CaII IR lines, and find that their photospheric components are well correlated in velocity and strength but that the corresponding HVFs show larger scatter. These results cannot be explained with ionization and/or thermal processes alone, and different mechanisms are required for the creation of HVF-forming regions in SNe Ia.
