scholarly journals Star Formation at Very Low Metallicity. II. On the Insignificance of Metal‐Line Cooling During the Early Stages of Gravitational Collapse

2007 ◽  
Vol 660 (2) ◽  
pp. 1332-1343 ◽  
Author(s):  
A.‐K. Jappsen ◽  
S. C. O. Glover ◽  
R. S. Klessen ◽  
M.‐M. Mac Low
Keyword(s):  
Star Formation ◽  
Gravitational Collapse ◽  
Metal Line ◽  
Early Stages ◽  
Low Metallicity

Detection of Molecular Clouds in the Magellanic Bridge: Candidate Star Formation Sites in a Nearby Low-Metallicity System

2006 ◽  
Vol 643 (2) ◽  
pp. L107-L110 ◽  
Author(s):  
N. Mizuno ◽  
E. Muller ◽  
H. Maeda ◽  
A. Kawamura ◽  
T. Minamidani ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Low Metallicity

scholarly journals On the role of the H2ortho:para ratio in gravitational collapse during star formation

2014 ◽  
Vol 563 ◽  
pp. A85 ◽  
Author(s):  
Neil Vaytet ◽  
Kengo Tomida ◽  
Gilles Chabrier
Keyword(s):  
Star Formation ◽  
Gravitational Collapse

scholarly journals Low Metallicity Galaxies at z ~ 0.7: Keys to the Origins of Metallicity Scaling Laws

2008 ◽  
Vol 4 (S255) ◽  
pp. 397-401
Author(s):  
David J. Rosario ◽  
Carlos Hoyos ◽  
David Koo ◽  
Andrew Phillips
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Galaxy Evolution ◽  
Scaling Laws ◽  
Temperature Sensitive ◽  
Star Forming ◽  
Low Metallicity ◽  
Emission Line Galaxies ◽  
Halo Masses ◽  
Stellar Masses

AbstractWe present a study of remarkably luminous and unique dwarf galaxies at redshifts of 0.5 < z < 0.7, selected from the DEEP2 Galaxy Redshift survey by the presence of the temperature sensitive [OIII]λ4363 emission line. Measurements of this important auroral line, as well as other strong oxygen lines, allow us to estimate the integrated oxygen abundances of these galaxies accurately without being subject to the degeneracy inherent in the standard R23 system used by most studies. [O/H] estimates range between 1/5–1/10 of the solar value. Not surprisingly, these systems are exceedingly rare and hence represent a population that is not typically present in local surveys such as SDSS, or smaller volume deep surveys such as GOODS.Our low-metallicity galaxies exhibit many unprecedented characteristics. With B-band luminosities close to L*, thse dwarfs lie significantly away from the luminosity-metallicity relationships of both local and intermediate redshift star-forming galaxies. Using stellar masses determined from optical and NIR photometry, we show that they also deviate strongly from corresponding mass-metallicity relationships. Their specific star formation rates are high, implying a significant burst of recent star formation. A campaign of high resolution spectroscopic follow-up shows that our galaxies have dynamical properties similar to local HII and compact emission line galaxies, but mass-to-light ratios that are much higher than average star-forming dwarfs.The low metallicities, high specific star formation rates, and small halo masses of our galaxies mark them as lower redshift analogs of Lyman-Break galaxies, which, at z ~ 2 are evolving onto the metallicity sequence that we observe in the galaxy population of today. In this sense, these systems offer fundamental insights into the physical processes and regulatory mechanisms that drive galaxy evolution in that epoch of major star formation and stellar mass assembly.

GLIMPSE Extended Green Objects and the Early Stages of Massive Star Formation

2014 ◽  
pp. 391-394
Author(s):  
Claudia J. Cyganowski ◽  
Crystal L. Brogan ◽  
Todd R. Hunter ◽  
Ed Churchwell ◽  
Barbara A. Whitney ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Star Formation ◽  
Early Stages

scholarly journals Possible Mechanisms of Single and Multiple Star Formation

1958 ◽  
Vol 8 ◽  
pp. 1017-1019
Author(s):  
G. J. Odgers ◽  
R. W. Stewart
Keyword(s):  
Star Formation ◽  
Dimensional Analysis ◽  
Gravitational Collapse ◽  
Gravitational Constant ◽  
Characteristic Velocity ◽  
Multiple Star ◽  
Typical Dimension ◽  
Jeans Criterion ◽  
Image Position

If we suppose that at least some stars are the result of the gravitational collapse of HI clouds, it seems necessary to consider Jeans' criterion. This can be derived by a number of arguments, but for our purpose it is sufficient to consider it a result of dimensional analysis, and we get where G is the gravitational constant, M is a typical dimension, and V is a characteristic velocity comprising all velocities interior to the region of gas being considered.

scholarly journals The Herschel Dwarf Galaxy Survey

2019 ◽  
Vol 626 ◽  
pp. A23 ◽  
Author(s):  
D. Cormier ◽  
N. P. Abel ◽  
S. Hony ◽  
V. Lebouteiller ◽  
S. C. Madden ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
Spectral Synthesis ◽  
Line Emission ◽  
Ionized Gas ◽  
Star Forming ◽  
Gas Phases ◽  
Physical Conditions ◽  
Radiation Fields ◽  
Low Metallicity

The sensitive infrared telescopes, Spitzer and Herschel, have been used to target low-metallicity star-forming galaxies, allowing us to investigate the properties of their interstellar medium (ISM) in unprecedented detail. Interpretation of the observations in physical terms relies on careful modeling of those properties. We have employed a multiphase approach to model the ISM phases (H II region and photodissociation region) with the spectral synthesis code Cloudy. Our goal is to characterize the physical conditions (gas densities, radiation fields, etc.) in the ISM of the galaxies from the Herschel Dwarf Galaxy Survey. We are particularly interested in correlations between those physical conditions and metallicity or star-formation activity. Other key issues we have addressed are the contribution of different ISM phases to the total line emission, especially of the [C II]157 μm line, and the characterization of the porosity of the ISM. We find that the lower-metallicity galaxies of our sample tend to have higher ionization parameters and galaxies with higher specific star-formation rates have higher gas densities. The [C II] emission arises mainly from PDRs and the contribution from the ionized gas phases is small, typically less than 30% of the observed emission. We also find a correlation – though with scatter – between metallicity and both the PDR covering factor and the fraction of [C II] from the ionized gas. Overall, the low metal abundances appear to be driving most of the changes in the ISM structure and conditions of these galaxies, and not the high specific star-formation rates. These results demonstrate in a quantitative way the increase of ISM porosity at low metallicity. Such porosity may be typical of galaxies in the young Universe.

scholarly journals DDO68-V1: an extremely metal-poor LBV in a void galaxy

2018 ◽  
Vol 14 (S344) ◽  
pp. 392-395
Author(s):  
Yulia Perepelitsyna ◽  
Simon Pustilnik
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Rare Event ◽  
Local Universe ◽  
Hii Region ◽  
V Band ◽  
Star Evolution ◽  
Low Metallicity ◽  
Massive Star Evolution

AbstractThe lowest metallicity massive stars in the Local Universe with $Z\sim \left( {{Z}_{\odot }}/50-{{Z}_{\odot }}/30 \right)$ are the crucial objects to test the validity of assumptions in the modern models of very low-metallicity massive star evolution. These models, in turn, have major implications for our understanding of galaxy and massive star formation in the early epochs. DDO68-V1 in a void galaxy DDO68 is a unique extremely metal-poor massive star. Discovered by us in 2008 in the HII region Knot3 with $Z={{Z}_{\odot }}/35\,\left[ 12+\log \left( \text{O/H} \right)\sim 7.14 \right]$, DDO68-V1 was identified as an LBV star. We present here the LBV lightcurve in V band, combining own new data and the last archive and/or literature data on the light of Knot3 over the 30 years. We find that during the years 2008-2011 the LBV have experienced a very rare event of ‘giant eruption’ with V-band amplitude of 4.5 mag ($V\sim {{24.5}^{m}}-{{20}^{m}}$).

Sign in / Sign up

Export Citation Format

Share Document