Spectroscopic investigation of objects of the Second Byurakan Survey. Stellar objects. V

Stepanyan, Dzh A.; Lipovetskii, V. A.; Chavushyan, V.; Erastova, L. K.; Shapovalova, A. I.

doi:10.1007/bf01004783

Cited by 9 publications

(6 citation statements)

References 1 publication

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“…This bright high redshift quasar (z em = 3.2, V=16.5) was discovered by Stepanian et al (1991). Our Keck spectrum for this object is of exceptionally high quality, with typical S/N reaching 120 per resolution element redward of Lyα emission.…”

Section: 9mentioning

confidence: 63%

Abundances at High Redshifts: The Chemical Enrichment History OF

Lü

Sargent

Barlow

et al. 1996

ApJS

377

462

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We study the elemental abundances of C, N, O, Al, Si, S, Cr, Mn, Fe, Ni, and Zn in a sample of 14 damped Lyα systems (galaxies) with H I column density N (H I)≥ 10 20 cm −2 , using high quality spectra of quasars obtained with the 10m Keck telescope. To ensure accuracy, only weak, unsaturated absorption lines are used to derive ion column densities and elemental abundances. Combining these abundance measurements with similar measurements in the literature, we investigate the chemical evolution of damped Lyα galaxies based on a sample of 23 systems in the redshift range 0.7 < z < 4.4. The main conclusions are as follows.1. The damped Lyα galaxies have (Fe/H) in the range of 1/10 to 1/300 solar, clearly indicating that these are young galaxies in the early stages of chemical evolution. The N (H I)-weighted mean metallicity of the damped Lyα galaxies between 2 < z < 3 is (Fe/H)=0.028 solar. There is a large scatter, about a factor of 30, in (Fe/H) at z < 3, which we argue probably results from the different formation histories of the absorbing galaxies or a mix of galaxy types.2. Comparisons of the distribution of (Fe/H) vs redshift for the sample of damped Lyα galaxies with the similar relation for the Milky Way disk indicate that the damped Lyα galaxies are much less metal-enriched than the Galactic disk in its past. Since there is evidence from our analyses that depletion of Fe by dust grains in the sample galaxies is relatively unimportant, the difference in the enrichment level between the sample of damped Lyα galaxies and the Milky Way disk suggests that damped Lyα galaxies are probably not high-redshift spiral disks in the traditional sense. Rather, they could represent a thick disk phase of galaxies, or more likely the spheroidal component of galaxies, or dwarf galaxies.3. The mean metallicity of the damped Lyα galaxies is found to increase with decreasing redshift, as is expected. All four of the damped Lyα galaxies at z > 3 in our sample have (Fe/H) around 1/100 solar or less. In comparison, a large fraction of the damped Lyα galaxies at z < 3 have reached ten times higher metallicity. This suggests that the time around z = 3 may be the epoch of galaxy formation in the sense that galaxies are beginning to form the bulk of their stars. Several other lines of evidence appear to point to the same conclusion, including the evolution of the neutral baryon 1 Hubble Fellow

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Section: 9mentioning

confidence: 63%

Abundances at High Redshifts: The Chemical Enrichment History OF

Lü

Sargent

Barlow

et al. 1996

ApJS

377

462

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“…J154359.3+535903 is also known as SBS 1542+541 as this source was discovered in the Second Byurakan Survey (Stepanyan et al 1991). It has many interesting properties: its BAL has a very high degree of ionization (Telfer et al 1998), an associated absorption system and damped Lyα (DLA) absorption system, and a strong X‐ray absorption (Green et al 2001).…”

Section: Resultsmentioning

confidence: 99%

Optical microvariability properties of BALQSOs

Joshi

Chand

Gupta

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present optical light curves of 19 radio quiet (RQ) broad absorption line (BAL) QSOs and study their rapid variability characteristics. Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to clearly detect any such microvariability exceeding 0.01--0.02 mag. Our observations cover a total of 13 nights (~72 hours) with each quasar monitored for about 4 hours on a given night. Our sample size is a factor of three larger than the number of radio-quiet BALQSOs previously searched for microvariability. We introduce a scaled F-test statistic for evaluating the presence of optical microvariability and demonstrate why it is generally preferable to the statistics usually employed for this purpose. Considering only unambiguous detections of microvariability we find that ~11 per cent of radio-quiet BALQSOs (two out of 19 sources) show microvariability for an individual observation length of about 4 hr. This new duty cycle of 11 per cent is similar to the usual low microvariability fraction of normal RQQSOs with observation lengths similar to those of ours. This result provides support for models where radio-quiet BALQSO do not appear to be a special case of the RQQSOs in terms of their microvariability properties.Comment: 13 pages, 3 figures, 3 tables, accepted for publication in MNRAS main journa

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“…The system SBS 0909+532 was discovered by Stepanyan et al (1991). Some years later, a collaboration between the Hamburger Sternwarte and the Harvard-Smithsonian Center for Astrophysics resolved the system into a pair of quasars (A and B) with a direct R-band flux ratio (at the same time of observation) ∆m = m B − m A = 0.58 mag and a separation of about 1.…”

Section: Introductionmentioning

confidence: 99%

Time delay of SBS 0909+532

Ullán

Goicoechea

Zheleznyak

et al. 2006

A&A

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Aims. The time delays between the components of a lensed quasar are basic tools for analysing the expansion of the Universe and the structure of the main lens galaxy halo. In this paper, we focus on the variability and time delay of the double system SBS 0909+532A,B as well as the time behaviour of the field stars. Methods. We use VR optical observations of SBS 0909+532A, B and the field stars in 2003. The frames were taken at Calar Alto, Maidanak, and Wise observatories, and the VR light curves of the field stars and quasar components were derived from aperture and point-spread function fitting methods. We measured the R-band time delay of the system from the χ 2 and dispersion techniques and 1000 synthetic light curves based on the observed records. Results. One nearby field star (SBS 0909+532c) was found to be variable, and the other two nearby field stars are non-variable sources. With respect to the quasar components, the R-band records seem more reliable and are more densely populated than the V-band ones. The observed R-band fluctuations permit a pre-conditioned measurement of the time delay. From the χ 2 minimization, if we assume that the quasar emission is observed first in B and afterwards in A (in agreement with basic observations of the system and the corresponding predictions), we obtain ∆τ BA = −45 +1 −11 days (95% confidence interval). The dispersion technique leads to a similar delay range. A by-product of the analysis is the determination of a totally corrected flux ratio in the R band (corrected by the time delay and the contamination due to the galaxy light). Our 95% measurement ∆m BA = m B (t + ∆τ BA ) − m A (t) = 0.575 ± 0.014 mag is in excellent agreement with previous results from contaminated fluxes at the same time of observation.

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Spectroscopic investigation of objects of the Second Byurakan Survey. Stellar objects. V

Cited by 9 publications

References 1 publication

Abundances at High Redshifts: The Chemical Enrichment History OF

Abundances at High Redshifts: The Chemical Enrichment History OF

Optical microvariability properties of BALQSOs

Time delay of SBS 0909+532

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