scholarly journals Do quasars evolve over cosmological time scales?

1986 ◽  
Vol 119 ◽  
pp. 439-445
Author(s):  
E.J. Wampler ◽  
D. Ponz
Keyword(s):  
Emission Line ◽  
Time Scales ◽  
Line Strength ◽  
Schmidt Telescope ◽  
Spectral Evolution ◽  
General Correlation ◽  
Cosmological Time ◽  
Systematic Biases ◽  
Evolution Laws ◽  
Lower Luminosity

Systematic biases that are redshift dependent can influence the optical discovery of quasars and the evolution laws derived from counts of quasars. New data and their interpretation for quasars brighter than MB = −24 in the Palomar Bright Quasar Survey (BQS) (Schmidt and Green, 1983) are consistent with no evolution. A comparison of BQS quasars with the brightest quasars from the CTIO Schmidt Telescope Survey (Osmer and Smith, 1980) shows that if qo is near zero, the co-moving density of bright quasars in a Friedmann cosmology is about 15 times higher for the CTIO survey quasars (mean z ≈ 2.8) than for the BQS quasars (mean z ≈ 1.8). In this case spectral evolution is also required since the CTIO quasars have stronger CIV λ1548 lines than the BQS quasars of similar luminosity. Alternatively, if qO is taken to be near 1, the CTIO survey quasars would then have lower luminosity than the BQS quasars and these data would be consistent with no evolution. Strong CIV λ1548 lines for the CTIO quasars would then fit the general correlation between absolute quasar luminosity and emission line strength (Wampler, Gaskell, Burke and Baldwin, 1984).

scholarly journals Galaxy Evolution in a Pilot Survey up toz=1and CDM Halos

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
E. Giraud ◽  
J. Melnick ◽  
Q.-S. Gu ◽  
H. Quintana ◽  
F. Selman ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Emission Lines ◽  
Pencil Beam ◽  
Spectral Evolution ◽  
Cosmological Time ◽  
Emission Line Galaxies ◽  
Individual Galaxy

We study spectral evolution of galaxies in a magnitude limited sample of 550 galaxies fromz=1down toz=0.3on a pencil beam of≈10′×10′. We concentrate on the large apparent cosmological structures along the line of sight, and we bin our individual galaxy spectra to obtain representative high S/N spectra based upon these structures. We divide the resulting average spectra in three groups to facilitate the analysis:galaxies with pure absorption line spectra, galaxies with emission lines and blue continua, and galaxies with emission lines and red continua. We revisit the question of downsizing in emission-line galaxies betweenz=0.9andz=0.45in our pencil-beam and find the following results: strong star formation in emission line galaxies, aging in emission line galaxies, and aging in absorption systems, are shifting from bright to faint systems as cosmological time increases. Each redshift bin is repopulated in new starbursts. Therefore at redshiftsz⩽1galaxy formation is downsizing both in luminosity and number density. Our observations indicate that atz⩽1star formation and hierarchical structure formation of CDM halos are not in phase.

scholarly journals An Automatic Approach for Selecting New HA Emission-Line Galaxies

1994 ◽  
Vol 161 ◽  
pp. 611-614
Author(s):  
O. Alonso ◽  
J. Zamorano ◽  
M. Rego ◽  
J. Gallego ◽  
A.G. Vitores
Keyword(s):  
Emission Line ◽  
Selection Criterion ◽  
Schmidt Telescope ◽  
Objective Prism ◽  
Emission Line Galaxies ◽  
Calar Alto ◽  
Observational Procedure

The most unambiguous way to discover new emission-line galaxies (ELGs) is directly by the presence of their lines, using objective-prism plates of adequate resolution. The first survey using this technique was developed by Smith in 1975 with the 0.6 m CTIO Curtis Schmidt Telescope. The Universidad Complutense de Madrid (UCM) is carrying out a survey of ELGs with the Schmidt Telescope at Calar Alto (Almería, Spain) using the presence of Ha in emission in IIIa-F prism plates as selection criterion. The observational procedure and results are described in Rego et al. 1989; Zamorano et al. 1990; Zamorano et al. 1993.

scholarly journals Deep Wide-field Hα Images of the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 95-96
Author(s):  
D. H. Morgan ◽  
Q. A. Parker ◽  
S. Phillipps
Keyword(s):  
Emission Line ◽  
Magellanic Clouds ◽  
Wide Area ◽  
Wide Field ◽  
Schmidt Telescope ◽  
Preliminary Results ◽  
Fine Grained ◽  
The Uk

A new Hα survey of the Magellanic Clouds which is being carried out on fine-grained Tech-Pan emulsion with the UK 1.2m Schmidt Telescope will have the best combination of depth and resolution of any that cover such a wide area in and around the Magellanic Clouds. Preliminary results show that the films will provide identifications of new emission-line stars and nebulae.

scholarly journals An Emission-Line Galaxy Survey with the UK Schmidt Telescope

1987 ◽  
Vol 121 ◽  
pp. 53-55
Author(s):  
M. Kalafi ◽  
A. Savage ◽  
A.R. Good ◽  
R.D. Cannon ◽  
M.G. Yates
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Preliminary Investigation ◽  
Schmidt Telescope ◽  
Large Area ◽  
Number Magnitude ◽  
Emission Line Galaxies ◽  
Galaxy Populations ◽  
The Uk ◽  
Line Galaxy

The use of objective prisms in conjunction with the large area coverage afforded by Schmidt telescopes provides a very powerful means of detecting large numbers of emission-line galaxies, and allows one to study their large scale distribution. An important question that has yet to be fully addressed is the relationship between the number-magnitude distributions of the normal field galaxy and emission-line galaxy populations. A comparison such as this would effectively probe the evolution with time of these active objects. For example, study of the distant (z = 0.458) cluster of galaxies associated with 3C 295 (Dressler & Gunn 1983) indicates that emission-line objects may have been far more numerous in the past than at present. As a preliminary investigation in advance of a larger project, we report here on a search for emission-line galaxies in four United Kingdom 1.2m Schmidt Telescope (UKST) objective prism fields.

scholarly journals Slitless Spectroscopy by Photographic and CCD Detectors Across Large Fields

1994 ◽  
Vol 161 ◽  
pp. 709-714
Author(s):  
G. Comte ◽  
C. Surace
Keyword(s):  
Emission Line ◽  
Emission Lines ◽  
Photographic Emulsion ◽  
Subsequent Reduction ◽  
Schmidt Telescope ◽  
Ccd Array ◽  
Objective Prism ◽  
Emission Line Galaxies ◽  
Ccd Detectors

We present a new survey of emission line galaxies, performed with the ESO 1 m Schmidt telescope equipped with the 4° objective prism using IIIa-J photographic emulsion. The plates are digitized with the MAMA microdensitometer. A subsequent reduction of the block scans gives redshifts with a mean accuracy of 160 km/s−1, and spectrophotometric measurements of the intensity and equivalent widths of the principal emission lines. A brief discussion is given of the possible extension of quantitative reduction of slitless spectroscopy to archive plates and future large CCD array frames.

Emission-line variability and the broad-line region of quasi-stellar objects. I - Time scales and photon densities

1987 ◽  
Vol 322 ◽  
pp. 164 ◽  
Author(s):  
Wei Zheng ◽  
E. Margaret Burbridge ◽  
Harding E. Smith ◽  
Ross D. Cohen ◽  
Steven E. Bradley
Keyword(s):  
Emission Line ◽  
Time Scales ◽  
Broad Line ◽  
Stellar Objects ◽  
Broad Line Region ◽  
Line Region ◽  
Quasi Stellar Objects

scholarly journals Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters

2020 ◽  
Vol 493 (4) ◽  
pp. 5120-5130 ◽  
Author(s):  
Michael V Maseda ◽  
Roland Bacon ◽  
Daniel Lam ◽  
Jorryt Matthee ◽  
Jarle Brinchmann ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Equivalent Width ◽  
Production Efficiency ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Photon Production ◽  
Efficient Production ◽  
Number Counts ◽  
Lower Luminosity

ABSTRACT While low-luminosity galaxies dominate number counts at all redshifts, their contribution to cosmic reionization is poorly understood due to a lack of knowledge of their physical properties. We isolate a sample of 35 z ≈ 4–5 continuum-faint Lyman-α emitters from deep VLT/MUSE spectroscopy and directly measure their H α emission using stacked Spitzer/IRAC Ch. 1 photometry. Based on Hubble Space Telescope imaging, we determine that the average UV continuum magnitude is fainter than −16 (≈ 0.01 L⋆), implying a median Lyman-α equivalent width of 259 Å. By combining the H α measurement with the UV magnitude, we determine the ionizing photon production efficiency, ξion, a first for such faint galaxies. The measurement of log10 (ξion [Hz erg−1]) = 26.28 ($^{+0.28}_{-0.40}$) is in excess of literature measurements of both continuum- and emission line-selected samples, implying a more efficient production of ionizing photons in these lower luminosity, Lyman-α-selected systems. We conclude that this elevated efficiency can be explained by stellar populations with metallicities between 4 × 10−4 and 0.008, with light-weighted ages less than 3 Myr.

Transition probabilities for lines arising from the 3d4 4p configuration of Cr(II)

1994 ◽  
Vol 72 (1-2) ◽  
pp. 57-60 ◽  
Author(s):  
A. M. Gonzalez ◽  
M. Ortiz ◽  
J. Campos
Keyword(s):  
Experimental Data ◽  
Emission Line ◽  
Sum Rules ◽  
Transition Probabilities ◽  
Line Strength ◽  
Line Intensities ◽  
Cr Content ◽  
Absolute Scale ◽  
Relative Transition ◽  
Thin Plasma

Relative transition probabilities for 43 lines arising from the 3d4 4p configuration of Cr(II) with cores 3d4 (5D), 3d4 (3P), and 3d4 (3H) were determined from measurements of emission-line intensities in a laser produced plasma. This experiment was carried out with Al–Cr alloys with a Cr content of about 0.1%, in order to have an optically thin plasma. Transition probabilities were placed on an absolute scale by using, where possible, accurate experimental lifetimes from the literature and line-strength sum rules. Comparison of the present results with the available theoretical and experimental data are made.

VARIABILITY PROPERTIES OF SWIFT-BAT GAMMA-RAY BURSTS

2011 ◽  
Vol 20 (10) ◽  
pp. 1969-1973 ◽  
Author(s):  
RAFFAELLA MARGUTTI ◽  
CRISTIANO GUIDORZI ◽  
GUIDO CHINCARINI
Keyword(s):  
Energy Range ◽  
Time Scales ◽  
Time Scale ◽  
Rest Frame ◽  
Gamma Ray ◽  
Timing Analysis ◽  
Gamma Ray Bursts ◽  
Cosmological Time ◽  
The Time Domain ◽  
Prompt Emission

We study the variability properties of the prompt emission of Gamma-Ray Bursts in the gamma-ray energy range. We use the power spectrum analysis in the time domain as developed by [Margutti, in preparation]; this technique is suitable to study the rms variations at different time scales. The timing analysis of 252 Swift light-curves in the 15–150 keV energy range reveals the existence of different variability classes. Moreover, after accounting for the cosmological time dilation, the distribution of the GRB characteristic variability time scales is found to cluster around 0.6–1 s we identify this time scale as a characteristic variability time scale of long GRBs in the source rest frame.

scholarly journals Some Results of an Hα Survey in the Taurus Dark Clouds

1998 ◽  
Vol 15 (1) ◽  
pp. 152-154
Author(s):  
Alisher S. Hojaev
Keyword(s):  
Emission Line ◽  
Schmidt Telescope ◽  
Byurakan Astrophysical Observatory ◽  
Dark Clouds ◽  
Objective Prism ◽  
Emission Stars ◽  
Additional Sample

AbstractFrom a series of 4° objective-prism plates obtained on the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory, 20 new Hα emission line stars were found. The intensity of Hα emission line was evaluated for these stars. An additional sample of probable Hα emission stars was also found. We present here details and some observational features of these stars. The total number of Hα emission line stars estimated for the surveyed area is about 80.

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