scholarly journals Dense cloud cores revealed by CO in the low metallicity dwarf galaxy WLM

Nature ◽  
2015 ◽  
Vol 525 (7568) ◽  
pp. 218-221 ◽  
Author(s):  
Monica Rubio ◽  
Bruce G. Elmegreen ◽  
Deidre A. Hunter ◽  
Elias Brinks ◽  
Juan R. Cortés ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Dense Cloud ◽  
Low Metallicity ◽  
Cloud Cores

scholarly journals Dense Cloud Cores revealed by ALMA CO observations in the low metallicity dwarf galaxy WLM

2016 ◽  
Vol 11 (S321) ◽  
pp. 229-231
Author(s):  
M. Rubio ◽  
B. Elmegreen ◽  
D. Hunter ◽  
J. Cortes ◽  
E. Brinks ◽  
...  
Keyword(s):  
Local Group ◽  
Dwarf Galaxy ◽  
Detection Threshold ◽  
Irregular Galaxy ◽  
Irregular Galaxies ◽  
Low Metallicity ◽  
Co Detection ◽  
Cloud Cores ◽  
Dwarf Irregular Galaxies ◽  
Co Observations

AbstractUnderstanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations, they are molecular with H2 the dominant species and CO the best available. When the abundances of carbon and oxygen are low compared to hydrogen, and the opacity from dust is also low, as in primeval galaxies and local dwarf irregular galaxies CO forms slowly and is easily destroyed, so it cannot accumulate inside dense clouds. Then we lose our ability to trace the gas in regions of star formation and we lose critical information on the temperatures, densities, and velocities of the material that collapses. I will report on high resolution observations with ALMA of CO clouds in the local group dwarf irregular galaxy WLM, which has a metallicity that is 13% of the solar value and 50% lower than the previous CO detection threshold and the properties derived of very small dense CO clouds mapped..

scholarly journals The Leoncino Dwarf Galaxy: Exploring the Low-metallicity End of the Luminosity–Metallicity and Mass–Metallicity Relations

2020 ◽  
Vol 891 (2) ◽  
pp. 181 ◽  
Author(s):  
Kristen. B. W. McQuinn ◽  
Danielle A. Berg ◽  
Evan D. Skillman ◽  
Elizabeth A. K. Adams ◽  
John M. Cannon ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Low Metallicity

scholarly journals The SAMI Galaxy Survey: the discovery of a luminous, low-metallicity H ii complex in the dwarf galaxy GAMA J141103.98−003242.3

2014 ◽  
Vol 445 (2) ◽  
pp. 1104-1113 ◽  
Author(s):  
S. N. Richards ◽  
A. L. Schaefer ◽  
Á. R. López-Sánchez ◽  
S. M. Croom ◽  
J. J. Bryant ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Low Metallicity

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.

C18O Observations of the Dense Cloud Cores and Star Formation in Ophiuchus

2000 ◽  
Vol 528 (2) ◽  
pp. 817-840 ◽  
Author(s):  
Kengo Tachihara ◽  
Akira Mizuno ◽  
Yasuo Fukui
Keyword(s):  
Star Formation ◽  
Dense Cloud ◽  
Cloud Cores

scholarly journals Environmental Mechanisms Shaping the Nature of Dwarf Spheroidal Galaxies: The View of Computer Simulations

2010 ◽  
Vol 2010 ◽  
pp. 1-21 ◽  
Author(s):  
Lucio Mayer
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Dwarf Galaxy ◽  
Feedback Mechanism ◽  
Gas Stripping ◽  
Morphological Transformation ◽  
Dwarf Spheroidal Galaxies ◽  
Tidal Forces ◽  
Ram Pressure ◽  
Low Metallicity

We review numerical works carried out over the last decade on the role of environmental mechanisms in shaping nature of the faintest galaxies known, dwarf spheroidals (dSphs). The combination of tidally induced morphological transformation, termed tidal stirring, with mass loss due to tidal and ram-pressure stripping aided by heating due to the cosmic ionizing background can turn late-type dwarfs resembling present-day dIrrs into classic dSphs. The time of infall into the primary halo is shown to be a key parameter. Dwarfs accreting at when the cosmic ultraviolet ionizing flux was much higher than today, and was thus able to keep the gas in the dwarfs warm and diffuse, were rapidly stripped of their baryons via ram pressure and tidal forces, producing very dark-matter-dominated objects with truncated star-formation histories, such as the Draco dSph. The low star-formation efficiency expected in such low-metallicity objects prior to their infall was crucial for keeping their disks gas dominated until stripping took over.Therefore gas stripping along with inefficient star-formation provides a new feedback mechanism, alternative to photoevaporation or supernovae feedback, playing a crucial role in dwarf galaxy formation and evolution. We also discuss how the ultra-faint dSphs belong to a different population of lower-mass dwarf satellites that were mostly shaped by reionization rather than by environmental mechanisms (“reionization fossils”). Finally, we scrutinize the various caveats in the current understanding of environmental effects as well as other recent ideas on the origin of Local Group dSphs.

scholarly journals Herschelphotometric observations of the low metallicity dwarf galaxy NGC 1705

2010 ◽  
Vol 518 ◽  
pp. L58 ◽  
Author(s):  
B. O'Halloran ◽  
M. Galametz ◽  
S. C. Madden ◽  
R. Auld ◽  
M. Baes ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Low Metallicity

scholarly journals The ISM of Low Metallicity Galaxies: The Herschel view

2012 ◽  
Vol 8 (S292) ◽  
pp. 127-134 ◽  
Author(s):  
Suzanne C. Madden ◽  
Aurélie Rémy ◽  
Frédéric Galliano ◽  
Maud Galametz ◽  
George Bendo ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Far Infrared ◽  
The Other ◽  
Spectral Energy ◽  
Molecular Gas ◽  
Mass Ratio ◽  
Energy Distributions ◽  
Local Universe ◽  
Low Metallicity ◽  
Fine Structure Lines

AbstractThe wide variety of low metallicity galaxies of the local universe serve as convenient laboratories to study the evolution of gas and dust and conditions for star formation in environments which may resemble those of the early universe. The Herschel Dwarf Galaxy Survey is studying the far infrared (FIR) and submillimeter (submm) properties of the gas and dust in galaxies with metallicity values as low as 1/45 that of solar. With complementary Spitzer, Laboca/APEX, Scuba/JCMT data, the dust spectral energy distributions are well constrained now, providing more accurate dust masses. We find a steep drop in dust-to-gas mass ratio (D/G) when the metallicity is below 12+log(O/H) ∼ 8. A submillimeter excess can be found in some low metallicity galaxies, which, when present, becomes apparent at wavelengths at or longer than 500 μm. While CO is difficult to observe in low metallicity gas, the FIR fine structure lines, on the other hand, are very luminous and highlight a potentially important reservoir of CO-free molecular gas, better traced by the 158 μm [CII] line.

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