The Space Density of Hot White Dwarfs

1983 ◽  
Vol 5 (2) ◽  
pp. 230-232
Author(s):  
Neill Reid ◽  
D.T. Wickramasinghe ◽  
M.S. Bessell
Keyword(s):  
Star Formation ◽  
Observational Studies ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Birth Rate ◽  
Main Sequence ◽  
Mass Density ◽  
Statistical Significance ◽  
Space Density ◽  
History Of

The space density of degenerate stars is an important parameter in Galactic Structure studies, not only because white dwarfs represent a significant fraction of the local mass density, but also because they act as tracers of the history of star formation (see e.g., Bessell 1978). Combining the present day luminosity function with theoretical cooling tracks allows constraints to be set on the birth rate of main sequence progenitors. However, since white dwarfs are intrinsically low luminosity objects, observational studies are hampered by difficulties in defining complete samples large enough to have statistical significance. This paper discusses preliminary results from one method of tackling this problem.

scholarly journals The Luminosity Function and Evolution of Cool White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 146-164 ◽  
Author(s):  
James Liebert
Keyword(s):  
Star Formation ◽  
White Dwarf ◽  
White Dwarfs ◽  
Luminosity Function ◽  
List Type ◽  
Type Number ◽  
Atmospheric Parameters ◽  
Theoretical Interest ◽  
History Of ◽  
Cool White Dwarfs

In the review, I attempt to focus on what we have recently learned from the observations about three general topics of great theoretical interest: 1. evidence for evolution of white dwarf surface abundances,2. the special problems of determining atmospheric parameters and abundances at the cool end of the sequence, and3. evidence for a peaking of the white dwarf luminosity function at Mbol = + 15 ± 1, with possible implications for cooling theory and the history of galactic star formation.

scholarly journals The Luminosity Function of White Dwarfs in the Local Disk and Halo

1989 ◽  
Vol 114 ◽  
pp. 15-23 ◽  
Author(s):  
James Liebert ◽  
Conard C. Dahn ◽  
David G. Monet
Keyword(s):  
White Dwarfs ◽  
Luminosity Function ◽  
Solar Neighborhood ◽  
Star Formation History ◽  
Empirical Estimates ◽  
Formation History ◽  
History Of ◽  
Cool White Dwarfs ◽  
Local Disk

The luminosity function (LF) and total space density of white dwarfs in the solar neighborhood contain important information about the star formation history of the stellar population, and provide an independent method of measuring its age. The first empirical estimates of the LF for degenerate stars were those of Weidemann (1967), Kovetz and Shaviv (1976) and Sion and Liebert (1977). The follow-up investigations made possible by the huge Luyten Palomar proper motion surveys, however, added many more faint white dwarfs to the known sample. While the number of known cool white dwarfs grew to nearly one hundred, these did not include any that were much fainter intrinsically than the coolest degenerates found from the early Luyten, van Biesbroeck and Eggen-Greenstein lists.

scholarly journals The Surface Density of Quasars

1978 ◽  
Vol 79 ◽  
pp. 295-303 ◽  
Author(s):  
J.G. Bolton ◽  
Ann Savage
Keyword(s):  
Surface Density ◽  
Luminosity Function ◽  
Statistical Significance ◽  
Comprehensive Investigation ◽  
Space Density ◽  
Close Pairs

A knowledge of the surface density of quasars as a function of magnitude is important for two reasons. Firstly it is necessary in order to assess the possible statistical significance of close pairs of quasars or the association between quasars and bright galaxies. Secondly it is a necessary step in the determination of the space density or luminosity function of QSOs. We have carried out what we believe to be currently the most comprehensive investigation into the surface density of quasars. Three techniques have been used in this investigation. These are

scholarly journals Derivation of the initial luminosity function and the past rate of star formation

1959 ◽  
Vol 10 ◽  
pp. 99-104
Author(s):  
M. Schmidt
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Main Sequence ◽  
Life Time ◽  
Interstellar Gas ◽  
The Past ◽  
Constant Rate

The initial luminosity function ψ(Mv) was introduced by Salpeter. He assumed uniform formation of stars and derived the initial luminosity function from the observed main-sequence luminosity function and the life time of a star of magnitude Mvon the main sequence. Recently van den Bergh considered the depletion of the interstellar gas by star formation. He found that at a constant rate of star formation the gas in the solar vicinity will be exhausted about 7 × 108years from now.

scholarly journals The star formation history of the Fornax dwarf spheroidal galaxy

2009 ◽  
Vol 5 (S262) ◽  
pp. 353-354
Author(s):  
Enrico V. Held ◽  
Eline Tolstoy ◽  
Luca Rizzi ◽  
Mary Cesetti ◽  
Andrew A. Cole ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Population ◽  
Main Sequence ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History ◽  
First Results ◽  
History Of

AbstractWe present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.

scholarly journals CALIFA survey: The spatially resolved star formation history of massive galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 300-303
Author(s):  
Rosa González Delgado ◽  
Enrique Pérez ◽  
Roberto Cid Fernandes ◽  
Rubén García-Benito ◽  
André de Amorim ◽  
...  
Keyword(s):  
Growth Rate ◽  
Star Formation ◽  
Galaxy Evolution ◽  
Local Density ◽  
Spectral Synthesis ◽  
Mass Density ◽  
Stellar Mass ◽  
Star Formation History ◽  
Formation History ◽  
History Of

AbstractThe Calar Alto Legacy Integral Field Area (CALIFA) project is an ongoing 3D spectroscopic survey of 600 nearby galaxies of all kinds. This pioneer survey is providing valuable clues on how galaxies form and evolve. Processed through spectral synthesis techniques, CALIFA datacubes allow us to, for the first time, spatially resolve the star formation history of galaxies spread across the color-magnitude diagram. The richness of this approach is already evident from the results obtained for the first ~ 1/6 of the sample. Here we show how the different galactic spatial sub-components (“bulge” and “disk”) grow their stellar mass over time. We explore the results stacking galaxies in mass bins, finding that, except at the lowest masses, galaxies grow inside-out, and that the growth rate depends on a galaxy's mass. The growth rate of inner and outer regions differ maximally at intermediate masses. We also find a good correlation between the age radial gradient and the stellar mass density, suggesting that the local density is a main driver of galaxy evolution.

scholarly journals Hypervelocity Stars. III. The Space Density and Ejection History of Main‐Sequence Stars from the Galactic Center

2007 ◽  
Vol 671 (2) ◽  
pp. 1708-1716 ◽  
Author(s):  
Warren R. Brown ◽  
Margaret J. Geller ◽  
Scott J. Kenyon ◽  
Michael J. Kurtz ◽  
Benjamin C. Bromley
Keyword(s):  
Main Sequence ◽  
Galactic Center ◽  
Main Sequence Stars ◽  
Space Density ◽  
History Of

scholarly journals Dissecting 30 Doradus: Optical and Near Infrared Star Formation History of the starburst cluster NGC2070 from the Hubble Tarantula Treasury Project

2015 ◽  
Vol 12 (S316) ◽  
pp. 77-83
Author(s):  
Michele Cignoni ◽  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Near Infrared ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
30 Doradus

AbstractI will present new results on the star formation history of 30 Doradus in the Large Magellanic Cloud based on the panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). Here the focus is on the starburst cluster NGC2070. The star formation history is derived by comparing the deepest ever optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PARSEC models, which include all stellar phases from pre-main sequence to post-main sequence. For the first time in this region we are able to measure the star formation using intermediate and low mass stars simultaneously. Our results suggest that NGC2070 experienced a prolonged activity. I will discuss the detailed star formation history, initial mass function and reddening distribution.

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