Search

Start Over Subject spectroscopy
421. CIV broad abs. line SDSS QSO obs. with Gemini
ID:
ivo://CDS.VizieR/J/ApJ/862/22
Title:
CIV broad abs. line SDSS QSO obs. with Gemini
Short Name:
J/ApJ/862/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We isolate a set of quasars that exhibit emergent CIV broad absorption lines (BALs) in their spectra by comparing spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 and the SDSS/BOSS Data Releases 9 and 10. After visually defining a set of emergent BALs, follow-up observations were obtained with the Gemini Observatory for 105 quasars. We find an emergence rate consistent with the previously reported disappearance rate of BAL quasars given the relative numbers of non-BAL and BAL quasars in the SDSS. We find that candidate newly emerged BALs are preferentially drawn from among BALs with smaller balnicity indices, shallower depths, larger velocities, and smaller widths. Within two rest-frame years (average) after a BAL has emerged, we find it equally likely to continue increasing in equivalent width in an observation 6 months later (average) as it is to start decreasing. From the time separations between our observations, we conclude that the coherence timescale of BALs is less than 100 rest-frame days. We observe coordinated variability among pairs of troughs in the same quasar, likely due to clouds at different velocities responding to the same changes in ionizing flux, and the coordination is stronger if the velocity separation between the two troughs is smaller. We speculate that the latter effect may be due to clouds having on average lower densities at higher velocities owing to mass conservation in an accelerating flow, causing the absorbing gas in those clouds to respond on different timescales to the same ionizing flux variations.
422. CIV candidates
ID:
ivo://CDS.VizieR/J/ApJ/708/868
Title:
CIV candidates
Short Name:
J/ApJ/708/868
Date:
21 Oct 2021
Publisher:
CDS
Description:
We surveyed the Hubble Space Telescope UV spectra of 49 low-redshift quasars for z<1 CIV candidates, relying solely on the characteristic wavelength separation of the doublet. After consideration of the defining traits of CIV doublets (e.g., consistent line profiles, other associated transitions, etc.), we defined a sample of 38 definite (group G=1) and five likely (G=2) doublets with rest equivalent widths W_r_ for both lines detected at >=3{sigma}_W_r__. We conducted Monte Carlo completeness tests to measure the unblocked redshift ({Delta}z) and co-moving path length ({Delta}X) over which we were sensitive to CIV doublets of a range of equivalent widths and column densities. Using the power-law model of f(N(C^+3^)), we measured the C^+3^ mass density relative to the critical density: {Omega}_C^+3^_=(6.20^+1.82^_-1.52_)x10^-8^ for 13<=logN(C^+3^)<=15.
423. CIV column densities in z<2.5 QSOs
ID:
ivo://CDS.VizieR/J/MNRAS/401/2715
Title:
CIV column densities in z<2.5 QSOs
Short Name:
J/MNRAS/401/2715
Date:
21 Oct 2021
Publisher:
CDS
Description:
The cosmic evolution of the metal content of the intergalactic medium puts stringent constraints on the properties of galactic outflows and on the nature of UV background. In this paper, we present a new measure of the redshift evolution of the mass density of CIV, {OMEGA}_CIV_, in the interval 1.5~<z~<4 based on a sample of more than 1500 CIV lines with column densities 10^12^~<N(CIV)~<10^15^cm^-2^. This sample more than doubles the absorption redshift path covered in the range z<2.5 by previous samples. The result shows a significant increase of {OMEGA}_CIV_ towards the lower redshifts at variance with the previously pictured constant behaviour.
424. CIV NAL systems from SDSS-DR14 quasar spectra
ID:
ivo://CDS.VizieR/J/ApJS/239/23
Title:
CIV NAL systems from SDSS-DR14 quasar spectra
Short Name:
J/ApJS/239/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the quasar spectra from the Sloan Digital Sky Survey, all with two-epoch to six-epoch observations, we search for CIV{lambda}{lambda}1548,1551 narrow absorption doublets in spectral data from the blue wing {upsilon}r=30000km/s until the red wing of CIV{lambda}1549 emission lines. We have obtained 21239 CIV narrow absorption line (NAL) systems, of which 647 systems were significantly changed on timescales from {Delta}MJD=0.24 to 1842.38 days at rest-frame. Both samples of the C IV NAL systems with multi-epoch observations and the variable C IV NAL systems are the largest ones to date. The offset velocity distribution of the variable C IV NALs from quasars has a peak at {upsilon}r~2000km/s and gently extends to a larger offset velocity. There are 110 variable C IV NALs with {upsilon}r>12000km/s. In addition, about 10% intrinsic C IV NALs show time variability on a timescale of <2000 days. We find that the variations of C IV NALs are positively or negatively correlated with the alternations of quasar continua. The two kinds of correlations suggest that the variable C IV NALs included in our absorber catalog can be classified into at least two populations: (1) highly ionized systems that are dominated by highly ionized absorbing gas and negatively respond to the fluctuations of quasar emissions; and (2) lowly ionized systems that are dominated by lowly ionized absorbing gas and positively respond to fluctuations of quasar emissions. We also find that the absolute fractional changes in the absorption strengths of C IV NALs are inversely correlated with absorption strengths.
425. CIV narrow absorption line systems in SDSS-DR14
ID:
ivo://CDS.VizieR/J/ApJS/236/39
Title:
CIV narrow absorption line systems in SDSS-DR14
Short Name:
J/ApJS/236/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
We assemble 207 variable quasars from the Sloan Digital Sky Survey, all with at least 3 observations, to analyze CIV narrow absorption doublets, and obtain 328 CIV narrow absorption line systems. We find that 19 out of 328 CIV narrow absorption line systems were changed by |{Delta}W_r_^{lambda}1548^|>=3{sigma}_{Delta}Wr_^{lambda}1548^ on timescales from 15.9 to 1477 days at rest-frame. Among the 19 obviously variable CIV systems, we find that (1) 14 systems have relative velocities {upsilon}_r_>0.01c and 4 systems have {upsilon}_r_>0.1c, where c is the speed of light; (2) 13 systems are accompanied by other variable CIV systems; (3) 9 systems were changed continuously during multiple observations; and (4) 1 system with {upsilon}_r_=16862km/s was enhanced by {Delta}W_r_^{lambda}1548^=2.7{sigma}_{Delta}Wr_^{lambda}1548^ in 0.67 day at rest-frame. The variations of absorption lines are inversely correlated with the changes in the ionizing continuum. We also find that large variations of CIV narrow absorption lines are form differently over a short timescale.
426. CIV QSO absorption systems
ID:
ivo://CDS.VizieR/J/A+A/283/759
Title:
CIV QSO absorption systems
Short Name:
J/A+A/283/759
Date:
21 Oct 2021
Publisher:
CDS
Description:
High spectral resolution (FWHM = 0.6 or 0.35 {AA}) were obtained for six high redshift QSOs, z_em_ > 2.2, containing lines from 31 metal-rich absorption line systems amongst which 20 Civ doublets split in subcomponents with velocity differences within a system smaller than 400 km.s^-1^. Our survey has been combined with published data at similar resolution and the resulting sample comprises 35 systems, 23 of which are splitted in a total of 87 subcomponents. The mean redshift of the sample is <z> = 2.65. The observations were carried out at the F/8 Cassegrain focus of the 3.6m telescope at la Silla, between 1984 and 1989.
427. CLAMATO DR1: 3D Ly{alpha} forest tomography
ID:
ivo://CDS.VizieR/J/ApJS/237/31
Title:
CLAMATO DR1: 3D Ly{alpha} forest tomography
Short Name:
J/ApJS/237/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
Faint star-forming galaxies at z~2-3 can be used as alternative background sources to probe the Ly{alpha} forest in addition to quasars, yielding high sightline densities that enable 3D tomographic reconstruction of the foreground absorption field. Here, we present the first data release from the COSMOS Ly{alpha} Mapping And Tomography Observations (CLAMATO) Survey, which was conducted with the LRIS spectrograph on the Keck I telescope. Over an observational footprint of 0.157deg^2^ within the COSMOS field, we used 240 galaxies and quasars at 2.17<z<3.00, with a mean comoving transverse separation of 2.37h^-1^Mpc, as background sources probing the foreground Ly{alpha} forest absorption at 2.05<z<2.55. The Ly{alpha} forest data was then used to create a Wiener-filtered tomographic reconstruction over a comoving volume of 3.15x10^5^h^-3^Mpc^3^ with an effective smoothing scale of 2.5h^-1^Mpc. In addition to traditional figures, this map is also presented as a virtual-reality visualization and manipulable interactive figure. We see large overdensities and underdensities that visually agree with the distribution of coeval galaxies from spectroscopic redshift surveys in the same field, including overdensities associated with several recently discovered galaxy protoclusters in the volume. Quantitatively, the map signal-to-noise is S/N^wiener^~3.4 over a 3h^-1^Mpc top-hat kernel based on the variances estimated from the Wiener filter. This data release includes the redshift catalog, reduced spectra, extracted Ly{alpha} forest pixel data, and reconstructed tomographic map of the absorption.
428. Cl 0024+16 and MS 0451-03 spectrophotometry
ID:
ivo://CDS.VizieR/J/ApJ/671/1503
Title:
Cl 0024+16 and MS 0451-03 spectrophotometry
Short Name:
J/ApJ/671/1503
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new results from our comparative survey of two massive, intermediate-redshift galaxy clusters, Cl 0024+17 (z=0.39) and MS 0451-03 (z=0.54). Combining optical and UV imaging with spectroscopy of member galaxies, we identify and study several key classes of "transition objects" whose stellar populations or dynamical states indicate a recent change in morphology and star formation rate. For the first time, we have been able to conclusively identify spiral galaxies in the process of transforming into S0 galaxies. This has been accomplished by locating both spirals whose star formation is being quenched and their eventual successors, the recently created S0s.
429. CLASH-VLT: the FF cluster MACS J0416.1-2403
ID:
ivo://CDS.VizieR/J/ApJS/224/33
Title:
CLASH-VLT: the FF cluster MACS J0416.1-2403
Short Name:
J/ApJS/224/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields (FF) cluster MACS J0416.1-2403 (z=0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over ~600arcmin^2^, including ~800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to ~2.2r_200_ (~4Mpc). Our analysis of substructures reveals a complex system composed of a main massive cluster (M_200_~0.9x10^15^M_{sun}_ and {sigma}_V,r200_~1000km/s) presenting two major features: (i) a bimodal velocity distribution, showing two central peaks separated by {Delta}V_rf_~1100km/s with comparable galaxy content and velocity dispersion, and (ii) a projected elongation of the main substructures along the NE-SW direction, with a prominent sub-clump ~600kpc SW of the center and an isolated BCG approximately halfway between the center and the SW clump. We also detect a low-mass structure at z~0.390, ~10' south of the cluster center, projected at ~3Mpc, with a relative line-of-sight velocity of {Delta}V_rf_~-1700km/s. The cluster mass profile that we obtain through our dynamical analysis deviates significantly from the "universal" NFW, being best fit by a Softened Isothermal Sphere model instead. The mass profile measured from the galaxy dynamics is found to be in relatively good agreement with those obtained from strong and weak lensing, as well as with that from the X-rays, despite the clearly unrelaxed nature of the cluster. Our results reveal an overall complex dynamical state of this massive cluster and support the hypothesis that the two main subclusters are being observed in a pre-collisional phase, in agreement with recent findings from radio and deep X-ray data. In this article, we also release the entire redshift catalog of 4386 sources in the field of this cluster, which includes 60 identified Chandra X-ray sources and 105 JVLA radio sources.
430. Classical Cepheids consistent radial velocities
ID:
ivo://CDS.VizieR/J/A+A/631/A37
Title:
Classical Cepheids consistent radial velocities
Short Name:
J/A+A/631/A37
Date:
21 Oct 2021
Publisher:
CDS
Description:
Accurate radial velocities (vrad) of Cepheids are mandatory within the context of Cepheid distance measurements using the Baade-Wesselink technique. The most common vrad derivation method consists in cross-correlating the observed stellar spectra with a binary template and measuring a velocity on the resulting mean profile. Nevertheless, for Cepheids and other pulsating stars, the spectral lines selected within the template as well as the way of fitting the cross-correlation function (CCF) have a direct and significant impact on the measured vrad. Our first aim is to detail the steps to compute consistent CCFs and vrad of Cepheids. Next, this study aims at characterising the impact of Cepheid spectral properties and vrad computation methods on the resulting line profiles and vrad time series. We collected more than 3900 high-resolution spectra from seven different spectrographs of 64 Classical Milky Way (MW) Cepheids. These spectra were normalised and standardised using a single custom-made process on pre-defined wavelength ranges.We built six tailored correlation templates selecting unblended spectral lines of different depths based on a synthetic Cepheid spectrum, on three different wavelength ranges from 3900 to 8000{AA}. Each observed spectrum was cross-correlated with these templates to build the corresponding CCFs, adopted as the proxy for the spectrum mean line profile. We derived a set of line profile observables as well as three different vrad measurements from each CCF and two custom proxies for the CCF quality and amount of signal. This study presents a large catalogue of consistent Cepheid CCFs and vrad time series. It confirms that each step of the process has a significant impact on the deduced vrad: the wavelength, the template line depth and width, and the vrad computation method. The way towards more robust Cepheid vrad time series seems to go through steps that minimise the asymmetry of the line profile and its impact on the vrad. Centroid or first-moment vrad, that exhibit slightly smaller amplitudes but significantly smaller scatter than Gaussian or biGaussian vrad, should therefore be favoured. Stronger or deeper spectral lines also tend to be less asymmetric and lead to more robust vrad than weaker lines.

Limit your search

more »

more »

more »

more »

more »