scholarly journals Star Formation Regulation, Gas Cycles and the chemical evolution of dwarf irregular galaxies

2007 ◽  
Vol 24 ◽  
pp. 101-106
Author(s):  
S. Recchi ◽  
G. Hensler
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

scholarly journals Gas Mixing, Gas Cycles and the Chemical Evolution of Dwarf Irregular Galaxies

2004 ◽  
Vol 217 ◽  
pp. 178-187 ◽  
Author(s):  
Gerhard Hensler ◽  
Joachim Köppen ◽  
Jan Pflamm ◽  
Andreas Rieschick
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Chemical Evolution ◽  
Dwarf Galaxies ◽  
Type Ii ◽  
Gas Mixing ◽  
Active Star ◽  
Active Star Formation ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

Dwarf galaxies are ideal laboratories to study influential effects on galaxy evolution. In particular, their gas-rich variant with very active star formation, starbursting dwarf irregulars, shows chemical and structural signatures that lead unambiguously to the conclusion that they are standing in a vital contact with their surroundings. Gas infall cannot only trigger star formation but also allows for a reduction of the metal content. on the other hand, active star formation ignites numerous supernovae type II which accumulate and can produce a galactic wind. This again depletes the metals pushing them into a gas mixing cycle with different timescales, locally of about 10 Myrs, but an galactic scales of at least 1 Gyr. This paper illuminates the different processes like gas infall and outflow and their effects on the chemical evolution, the star formation, and the gas mixing in dwarf irregular galaxies.

scholarly journals HI Distribution in Extreme Dwarf Irregulars and Dwarf Spheroidals

1998 ◽  
Vol 11 (1) ◽  
pp. 121-122
Author(s):  
Claude Carignan
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Large Fraction ◽  
Dwarf Spheroidal Galaxies ◽  
Irregular Galaxies ◽  
Single Burst ◽  
Dwarf Spheroidals ◽  
Dwarf Irregular Galaxies ◽  
Spheroidal Galaxies

Recent studies (Puche & Westpfahl 1994, Young & Lo 1996) have shown that the distribution of HI in some extreme low luminosity dwarf irregular galaxies (e.g. M81dwA, Holmberg I, Leo A) tends to have a ring-like (or shell-like) distribution which suggests that a single burst of star formation could expell most of the remaining ISM (or at least a large fraction of it) from the system. In view of this, Puche & Westpfahl (1994) suggested that in dwarf spheroidal galaxies, the HI should be found at large radii since no young stellar population is observed in most of them.

Stellar feedback in dwarf irregular galaxies with radio continuum observations

2018 ◽  
Vol 14 (S344) ◽  
pp. 255-258
Author(s):  
Volker Heesen ◽  
Aritra Basu ◽  
Elias Brinks ◽  
George Heald ◽  
Andrew Fletcher ◽  
...  
Keyword(s):  
Star Formation ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Very Large Array ◽  
Radio Halo ◽  
Spatially Resolved ◽  
Ic 10 ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

AbstractLow-mass dwarf irregular galaxies are subject to outflows, in which cosmic rays may play a very important role; they can be traced via their electron component, the cosmic ray electrons (CRe), in the radio continuum as non-thermal synchrotron emission. With the advent of sensitive low-frequency observations, such as with the Low-Frequency Array (LOFAR), we can trace CRe far away from star formation sites. Together with GHz-observations, such as with the Very Large Array (VLA), we can study spatially resolved radio continuum spectra at matched angular resolution and sensitivity. Here, we present results from our 6-GHz VLA survey of 40 nearby dwarf galaxies and our LOFAR study of the nearby starburst dwarf irregular galaxy IC 10. We explore the relation of RC emission with star formation tracers and study in IC 10 the nature of a low-frequency radio halo, which we find to be the result of a galactic wind.

scholarly journals A new method to derive star formation histories in dwarf galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 267-270
Author(s):  
Marius Čeponis ◽  
Rima Stonkutė ◽  
Vladas Vansevičius
Keyword(s):  
Star Formation ◽  
New Method ◽  
Star Forming ◽  
Stellar Photometry ◽  
Star Forming Regions ◽  
Density Maps ◽  
Irregular Galaxies ◽  
Star Formation Histories ◽  
Dwarf Irregular Galaxies ◽  
Inside Out

AbstractWe present a new method to derive 2D star formation histories in dwarf irregular galaxies. Based on multicolor stellar photometry data we have found that in the Leo A galaxy during the last ∽400 Myr star formation was propagating according to the inside-out scenario. Star-forming regions have spread strongly asymmetrically from the center and their present day distribution correlates well with the Hi surface density maps.

Star formation in dwarf irregular galaxies - DDO 210 and NGC 3109

1993 ◽  
Vol 105 ◽  
pp. 894 ◽  
Author(s):  
L. Greggio ◽  
G. Marconi ◽  
M. Tosi ◽  
P. Focardi
Keyword(s):  
Star Formation ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

scholarly journals The relation between atomic gas and star formation rate densities in faint dwarf irregular galaxies

2014 ◽  
Vol 445 (2) ◽  
pp. 1392-1402 ◽  
Author(s):  
Sambit Roychowdhury ◽  
Jayaram N. Chengalur ◽  
Serafim S. Kaisin ◽  
Igor D. Karachentsev
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Irregular Galaxies ◽  
Atomic Gas ◽  
Dwarf Irregular Galaxies

scholarly journals Testing Evolutionary Models of Dwarf Irregular Galaxies through Gas and Stellar Metallicity Determinations in HII Galaxies

2012 ◽  
Vol 8 (S292) ◽  
pp. 254-254
Author(s):  
Pieter Westera ◽  
François Cuisinier ◽  
Didier Curty ◽  
Roland Buser
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Line Strength ◽  
Star Formation History ◽  
High Mass ◽  
Evolutionary Models ◽  
Homogeneous Sample ◽  
Irregular Galaxies ◽  
Low Metallicity ◽  
Dwarf Irregular Galaxies

AbstractDwarf irregular galaxies are usually low-metallicity objects, and show ongoing or very recent star formation, giving rise to their irregular appearance. Especially HII galaxies, a sub-category of dwarf irregulars showing unusually high star formation activity, are believed to be among the least evolved galaxies in existence today. Therefore, they are very interesting objects for studies of early galaxy evolution and of metallicity enrichment mechanisms.Several groups have developed theoretical evolutionary models of galaxies of this type, describing different possible formation and evolutionary scenarii, and varying factors such as gas infall and outflow, as well as the star formation history, and making predictions about their chemical evolution. One way to evaluate these models is by determining the metallicities of the different components of these galaxies, their gas and stars.We examine a sample of HII galaxies from the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of HII galaxy spectra to date. Using very restrictive selection criteria, which guarantee a sample of high quality spectra and avoid “contamination” by spectra of objects of other nature, we defined a sample of ∼ 700 HII galaxies spectra.Through emission line strength calibrations and a detailed stellar population synthesis, we determined the metallicities of both the gas and the stellar content of these galaxies.For HII galaxies up to stellar masses of 5 × 109M⊙, we find enrichment mechanisms not to vary with galactic mass, being the same for low- and high-mass galaxies on average. They do seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history. Our results favour galaxy evolutionary models featuring constantly infalling low-metallicity clouds that retain part of the galactic winds. Above 5 × 109M⊙ stellar mass, the retention of high metallicity gas by the galaxies' gravitational potential dominates.I would like to thank the Fundação de Amparo à Pesquisa do Estado do São Paulo (FAPESP) for financial support.

scholarly journals Star formation histories in dwarf irregular galaxies in the Local Group

1991 ◽  
Vol 148 ◽  
pp. 343-344
Author(s):  
L. Greggio ◽  
G. Marconi ◽  
P. Focardi ◽  
M. Tosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Mass Function ◽  
Initial Mass Function ◽  
Main Sequence Stars ◽  
Star Formation Activity ◽  
Irregular Galaxies ◽  
Ccd Observations ◽  
Star Formation Histories ◽  
Dwarf Irregular Galaxies

The process of star formation (SF) and the modalities with which it occurs in galaxies of different sizes are still poorly understood. On the other hand, interpretation of the chemical and photometric properties of galaxies requires the adoption of adequate laws for the SF rate and Initial Mass Function (IMF) in model computations. Dwarf irregular galaxies in the Local Group offer the chance to study their SF history through analysis of their HR diagrams, which can be derived down to V 25, corresponding to MV0, i.e. to main sequence stars of 2 M⊙. Therefore, for these galaxies, we can derive information on the star formation activity which has occurred over the last 1 Gyr approximately. In this framework, we have undertaken CCD observations of Dwarf irregular galaxies in the Local Group with ESO telescopes and briefly present here the results obtained for DDO 210, Sextans B and NGC 3109.

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