High-resolution spectroscopy of selected absorption lines toward quasi-stellar objects. II - The metal-to-hydrogen ratio in a 'metal-free' cloud toward S5 0014 + 81

ABSTRACT We investigate the spectroscopic optical properties of gamma-ray sources detected with high significance above 50 GeV in the Third Catalog of Hard Fermi-LAT Sources and that are good candidates as TeV emitters. We focus on the 91 sources that are labelled by the Fermi team as BL Lac (BLL) objects or blazar candidates of uncertain type (BCUs), are in the Northern hemisphere, and are with unknown or uncertain redshift. We report here on GTC (Gran Telescopio Canarias) spectra (in the spectral range 4100–7750 Å) of 13 BCUs and 42 BLL objects. We are able to classify the observed targets as BLL objects and each source is briefly discussed. The spectra allowed us to determine the redshift of 25 objects on the basis of emission and/or absorption lines, finding 0.05 < z < 0.91. Most of the emission lines detected are due to forbidden transition of [O iii] and [N ii]. The observed line luminosity is found to be lower than that of quasi-stellar objects (QSOs) at similar continuum and could be reconciled with the line–continuum luminosity relationship of QSOs if a significant beaming factor is assumed. Moreover, for five sources we found intervening absorption lines that allow to set a spectroscopic lower limit of the redshift. For the remaining 25 sources, for which the spectra are lineless, a lower limit to z is given, assuming that the host galaxies are giant ellipticals.

Download Full-text

Absorption Lines in Quasi-stellar Objects

Nature ◽

10.1038/2161092a0 ◽

1967 ◽

Vol 216 (5120) ◽

pp. 1092-1092 ◽

Cited By ~ 1

Author(s):

G. R. BURBIDGE ◽

E. M. BURBIDGE

Keyword(s):

Absorption Lines ◽

Stellar Objects ◽

Quasi Stellar Objects

Download Full-text

AHubble Space TelescopeFaint Object Spectrograph Survey for Broad Absorption Lines in a Sample of Low‐Redshift Weak [Oiii] Quasi‐stellar Objects

The Astrophysical Journal ◽

10.1086/303610 ◽

1997 ◽

Vol 476 (1) ◽

pp. 40-48 ◽

Cited By ~ 40

Author(s):

David A. Turnshek ◽

Eric M. Monier ◽

Christopher J. Sirola ◽

Brian R. Espey

Keyword(s):

Absorption Lines ◽

Broad Absorption ◽

Stellar Objects ◽

Quasi Stellar Objects ◽

Broad Absorption Lines

Download Full-text

Sizes of Intervening C IV Absorbers from High Resolution Spectroscopy of APM 0827+5255

Symposium - International Astronomical Union ◽

10.1017/s0074180900197724 ◽

2004 ◽

Vol 217 ◽

pp. 272-274

Author(s):

Panayiotis Tzanavaris ◽

Robert F. Carswell

Keyword(s):

High Resolution ◽

Lower Limit ◽

Absorption Lines ◽

High Resolution Spectroscopy ◽

Line Of Sight ◽

Total Coverage ◽

Best Estimates

Some intervening C IV absorbers in the Keck/HIRES spectrum of APM 0827+5255 give rise to absorption lines for which the observed optical depths for the doublet components are not in the expected 2 : 1 ratio. We model this effect as coverage of one line of sight to this gravitationally lensed quasar and perform a set of simulations to select a sample of lines for which our model provides an explanation for the effect. We use lines in this sample to obtain estimates for minimum absorber sizes from total coverage and the separations of the lines of sight for a range of lens redshifts, z1, and two cosmologies. We also obtain best estimates for overall sizes from a statistical “hit and miss” approach. For z1 = 0.7 our results set a lower limit to sizes of C IV absorbers of ~ 0.3 h−172 kpc (~ 0.5 h−172 kpc) for ΩM = 1, ΩA = 0 (ΩM = 0.3, ΩA = 0.7).

Download Full-text

Interstellar Matter with Very Large Telescopes

International Astronomical Union Colloquium ◽

10.1017/s0252921100108772 ◽

1984 ◽

Vol 79 ◽

pp. 675-678

Author(s):

J. Lequeux

Keyword(s):

High Resolution ◽

Absorption Lines ◽

High Resolution Spectroscopy ◽

Interstellar Matter ◽

Large Telescope ◽

Interstellar Absorption ◽

Near Ir ◽

Very Large Telescope ◽

Large Telescopes ◽

Diffuse Matter

Interstellar matter is certainly one of the fields where a very large telescope (VLT) will prove to be most fruitful. This includes (somewhat paradoxically, but this will be explained later) the study of extended emissions. I will now examine in turn the different domains of interest for a VLT.I. Neutral diffuse matterOptical and near IR observations will mainly contribute to this domain through high-resolution spectroscopy of interstellar absorption lines in the spectra of stars. These lines are resonant lines of atoms (NaI, KI, etc.) or ions (CaII, TiII, etc.) as well as of some molecules (CH+, CH, CN, CS+, C2 in the near IR). Clearly this kind of study is always photon - limited; a VLT will collect more photons than present telescopes, thus increase the possibilities considerably.

Download Full-text