- ID:
- ivo://CDS.VizieR/J/MNRAS/351/83
- Title:
- Blazars equivalent widths and radio luminosity
- Short Name:
- J/MNRAS/351/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars based on the strength of their emission lines. This is performed rather arbitrarily by defining a diagonal line in the Ca H&K break value-equivalent width plane, following Marcha et al. (1996MNRAS.281..425M). We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS, Cat. <J/AJ/115/1253> and <J/MNRAS/323/757>) and 2-Jy radio survey and find a significant bimodality for the narrow emission line [OIII]{lambda}5007. This suggests the presence of two physically distinct classes of radio-loud active galactic nuclei (AGN). We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII]{lambda}5007-[OII]{lambda}3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars.
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- ID:
- ivo://CDS.VizieR/J/ApJ/861/130
- Title:
- BL Lac objects GTC low resolution spectroscopy
- Short Name:
- J/ApJ/861/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on 16 BL Lacertae objects that were proposed to be at z>1. We present spectroscopic observations secured at the 10.4m GTC that allowed us to assess the redshift of these sources. In particular, for five objects, we disprove the previous value of the redshift reported in the literature and found that they lie at z<1. Moreover, two of them exhibit broad emission lines that are not characteristic of BL Lacertae objects. On the other hand, for eight targets, we improve the tentative value of z, previously based on only one feature, by detecting a number of emission lines. Finally, in three cases, we detect the onset of the Ly{alpha} forest at z>2.50. Based on the new high quality spectra, we found that only half of the observed objects can be classified as bona-fide BL Lacs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/195
- Title:
- Blue and red spectra of {omega} Cen HB stars
- Short Name:
- J/MNRAS/399/195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The multiphase interstellar medium (ISM) is highly structured, on scales from the size of the Solar System to that of a galaxy. In particular, small-scale structures are difficult to study and hence are poorly understood. We used the multiplex capabilities of the AAOmega spectrograph at the Anglo-Australian Telescope to create a half-square-degree map of the neutral and low-ionized ISM in front of the nearby (~5kpc), most massive Galactic globular cluster, {omega} Centauri. Its redshifted, metal-poor and hot horizontal branch stars probe the medium-strong CaII K and NaI D2 line absorption, and weak absorption in the {lambda}5780 and {lambda}5797 diffuse interstellar bands (DIBs), on scales around a parsec. The kinematical and thermodynamical picture emerging from these data is that we predominantly probe the warm neutral medium and weakly ionized medium of the Galactic Disc-Halo interface, ~0.3-1kpc above the mid-plane. A comparison with Spitzer Space Telescope 24um and DIRBE/IRAS maps of the warm and cold dust emission confirms that both NaI and CaII trace the overall column density of the warm neutral and weakly ionized medium. Clear signatures are seen of the depletion of calcium atoms from the gas phase into dust grains.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/110
- Title:
- Boo-127 and Boo-980 high-resolution spectra
- Short Name:
- J/ApJ/826/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundance measurements of two metal-poor red giant stars in the ultra-faint dwarf galaxy Bootes I, based on Magellan/MIKE high-resolution spectra. For Boo-980, with [Fe/H]=-3.1 , we present the first elemental abundance measurements, while Boo-127, with [Fe/H]=-2.0 , shows abundances in good agreement with previous measurements. Light and iron-peak element abundance ratios in the two Bootes I stars, as well as those of most other Bootes I members, collected from the literature, closely resemble those of regular metal-poor halo stars. Neutron-capture element abundances Sr and Ba are systematically lower than the main halo trend and also show a significant abundance spread. Overall, this is similar to what has been found for other ultra-faint dwarf galaxies. We apply corrections to the carbon abundances (commensurate with stellar evolutionary status) of the entire sample and find 21% of stars to be carbon-enhanced metal-poor (CEMP) stars, compared to 13% without using the carbon correction. We reassess the metallicity distribution functions for the CEMP stars and non-CEMP stars, and confirm earlier claims that CEMP stars might belong to a different, earlier population. Applying a set of abundance criteria to test to what extent Bootes I could be a surviving first galaxy suggests that it is one of the earliest assembled systems that perhaps received gas from accretion from other clouds in the system, or from swallowing a first galaxy or building block type object. This resulted in the two stellar populations observable today.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2980
- Title:
- BOSS narrow CIV absorption lines. III.
- Short Name:
- J/MNRAS/462/2980
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we extend our work of IV {lambda}{lambda}1548,1551 narrow absorption lines (NALs) with z_abs_<<z_em_ on quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS) to collect CIV NALs with z_abs_<=z_em_ from blue to red wings of CIV {lambda}1549 emission lines. Together with IV NALs with 1.4544<=z_abs_<=4.9224 in surveyed spectral region redward of Ly{alpha} until red wing of CIV {lambda}1549 emission line. We find that the stronger CIV NALs tend to be the more saturated absorptions, and associated systems (z_abs_~=z_em_) seem to have larger absorption strengths when compared to intervening ones (z_abs_<<z_em_). The redshift density evolution behaviour of absorbers (the number of absorbers per redshift path) is similar to the history of the cosmic star formation. When compared to the quasar-frame velocity ({beta}) distribution of MgII absorbers, the {beta} distribution of CIV absorbers is broader at {beta}~=0, shows longer extended tail, and exhibits a larger dispersion for environmental absorptions. In addition, for associated CIV absorbers, we find that low-luminosity quasars seem to exhibit smaller {beta} and stronger absorptions when compared to high-luminosity quasars.
- ID:
- ivo://CDS.VizieR/J/ApJS/215/12
- Title:
- BOSS narrow CIV absorption lines. II. zem>2.4
- Short Name:
- J/ApJS/215/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As the second work in a series of papers aiming to detect absorption systems in the quasar spectra of the Baryon Oscillation Spectroscopic Survey, we continue the analysis of Paper I (Chen+, 2014, J/ApJS/210/7; 2014ApJS..212...17C) by expanding the quasar sample to those quasars with z_em_>2.4. This yields a sample of 21963 appropriate quasars to search for narrow CIV{lambda}{lambda}1548,1551 absorptions with W_r_>=0.2{AA} for both lines. There are 9708 quasars with at least one appropriate absorption system imprinted on their spectra. From these spectra, we detect 13919 narrow C IV absorption systems whose absorption redshifts cover a range of z_abs_=1.8784-4.3704. In this paper and Paper I, we have selected 37241 appropriate quasars with median S/N>=4 and 1.54<~z_em_<~5.16 to visually analyze narrow CIV{lambda}{lambda}1548,1551 absorption doublets one by one. A total of 15999 quasars are found to have at least one appropriate absorption system imprinted on their spectra. From these 15999 quasar spectra, we have detected 23336 appropriate CIV{lambda}{lambda}1548,1551 absorption systems with W_r_>=0.2{AA} whose absorption redshifts cover a range of z_abs_=1.4544-4.3704. The largest values of W_r_ are 3.19{AA} for the {lambda}1548 absorption line and 2.93{AA} for the {lambda}1551 absorption line, respectively. We find that only a few absorbers show large values of W_r_. About 1.1% of the total absorbers have W_r_{lambda}1548>=2.0{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJS/210/7
- Title:
- BOSS narrow CIV absorption lines. I. zem<=2.4
- Short Name:
- J/ApJS/210/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled absorption systems by visually identifying CIV {lambda}{lambda}1548, 1551 absorption doublets in the quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS) one by one. This paper is the first of the series of work. In this paper, we focus on quasars with relatively low redshifts and high signal-to-noise ratio spectra, and hence we limit our analysis to quasars with z_em_<=2.4 and to doublets with W_r_{lambda}1548>=0.2{AA}. Out of the more than 87000 quasars in Data Release 9, we limit our search to 10121 quasars that have the appropriate redshifts and spectra with high enough signal-to-noise ratios to identify narrow CIV absorption lines. Among them, 5442 quasars are detected to have at least one CIV {lambda}{lambda}1548, 1551 absorption doublet. We obtain a catalog containing 8368 CIV {lambda}{lambda}1548, 1551 absorption systems, whose redshifts are within z_abs_=1.4544-2.2805. In this catalog, about 33.7% absorbers have 0.2{AA}<=W_r_{lambda}1548<0.5{AA}, about 45.9% absorbers have 0.5{AA}<=W_r_{lambda}1548<1.0{AA}, about 19.2% absorbers have 1.0{AA}<=W_r_{lambda}1548<2.0{AA}, and about 1.2% absorbers have W_r_{lambda}1548>=2.0{AA}.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A51
- Title:
- 185 bright XMM-CDFS sources spectral properties
- Short Name:
- J/A+A/639/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray spectra of 185 bright sources detected in the XMM-Newton deep survey of the Chandra Deep Field South, combining the three EPIC cameras. The 2-10keV flux limit of the sample is 2x10^-15^erg/s/cm^2^. The sources are distributed over a redshift range of z=0.1-3.8. Eleven new X-ray redshift measurements are included. A spectral analysis was performed using a simple model to obtain absorbing column densities, rest-frame 2-10keV luminosities and Fe K line properties of 180 sources at z>0.4. Obscured AGN are found to be more abundant toward higher redshifts. Using the XMM-Newton data alone, seven Compton-thick AGN candidates are identified, which makes the Compton-thick AGN fraction to be ~=4%. An exploratory spectral inspection method with two rest-frame X-ray colours and an Fe line strength indicator is introduced and tested against the results from spectral fitting. This method works reasonably well to characterise a spectral shape and can be useful for a pre-selection of Compton-thick AGN candidates.We found six objects exhibiting broad Fe K lines out of 21 unobscured AGN of best data quality, implying a detection rate of 30%. Five redshift spikes, each of which has more than six sources, are identified in the redshift distribution of the X-ray sources. Contrary to the overall trend, the sources at the two higher-redshift spikes at z=1.61 and z=2.57 have puzzlingly low obscuration.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/73
- Title:
- Brown dwarf surface gravities with Keck/NIRSPEC
- Short Name:
- J/ApJ/838/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine 131 new medium-resolution (R~2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass stars and brown dwarfs spanning spectral types M5-T9. Specifically, we use an established set of spectral indices to determine surface gravity classifications for all of the M6-L7 objects in our sample by measuring the equivalent widths (EW) of the K I lines at 1.1692, 1.1778, and 1.2529{mu}m, and the 1.2{mu}m FeH_J_ absorption index. Our results are consistent with previous surface gravity measurements, showing a distinct double peak-at ~L5 and T5-in K I EW as a function of spectral type. We analyze the K I EWs of 73 objects of known ages and find a linear trend between log(Age) and EW. From this relationship, we assign age ranges to the very low gravity, intermediate gravity, and field gravity designations for spectral types M6-L0. Interestingly, the ages probed by these designations remain broad, change with spectral type, and depend on the gravity-sensitive index used. Gravity designations are useful indicators of the possibility of youth, but current data sets cannot be used to provide a precise age estimate.
- ID:
- ivo://CDS.VizieR/J/A+A/434/1125
- Title:
- B-type Supergiants in the SMC
- Short Name:
- J/A+A/434/1125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution UCLES/AAT spectra are presented for nine B-type supergiants in the SMC, chosen on the basis that they may show varying amounts of nuclear-synthetically processed material mixed to their surface. These spectra have been analysed using a new grid of approximately 12000 non-LTE line blanketed TLUSTY model atmospheres to estimate atmospheric parameters and chemical composition.
