scholarly journals Radial variations of the SFHs of dwarf irregular galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 345-348
Author(s):  
Hong-Xin Zhang ◽  
Deidre A. Hunter ◽  
Bruce G. Elmegreen ◽  
Yu Gao ◽  
Andreas Schruba
Keyword(s):  
Line Emission ◽  
Star Forming ◽  
The Past ◽  
Irregular Galaxies ◽  
Double Exponential ◽  
Multi Wavelength ◽  
Disk Growth ◽  
Dwarf Irregular Galaxies ◽  
Inside Out ◽  
Hubble Time

AbstractThe LITTLE THINGS project† has compiled multi-wavelength data (including VLA hi-line emission maps, GALEX FUV/NUV imagery, UBV, narrow-band Hα, and Spitzer images) for a representative sample of nearby dwarf irregular (dIrr) galaxies. The broadband data are used to constrain the radial variations of the star formation (SF) rate (SFR) averaged over the past 0.1 Gyr, 1 Gyr and a Hubble time, with a complete library of model SF histories (SFHs). The recent SF of more than ~ 80% of the dIrrs in our sample has been concentrated in the inner disk, and the SF in the outer disk has been markedly suppressed. This outside-in shrinking of the star-forming disk leaves a down-bending (double exponential) stellar mass surface density (Σ*) distribution. Our findings in dIrrs are in contrast to the inside-out disk growth scenario suggested for luminous spiral galaxies.

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.

scholarly journals Angular Momentum Accretion onto Disc Galaxies

2018 ◽  
Vol 14 (A30) ◽  
pp. 228-232
Author(s):  
Filippo Fraternali ◽  
Gabriele Pezzulli
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Momentum Distribution ◽  
Intergalactic Medium ◽  
Star Forming ◽  
Gas Accretion ◽  
Hot Corona ◽  
Inside Out ◽  
Disc Galaxies ◽  
Hubble Time

AbstractThroughout the Hubble time, gas makes its way from the intergalactic medium into galaxies fuelling their star formation and promoting their growth. One of the key properties of the accreting gas is its angular momentum, which has profound implications for the evolution of, in particular, disc galaxies. Here, we discuss how to infer the angular momentum of the accreting gas using observations of present-day galaxy discs. We first summarize evidence for ongoing inside-out growth of star forming discs. We then focus on the chemistry of the discs and show how the observed metallicity gradients can be explained if gas accretes onto a disc rotating with a velocity 20 – 30% lower than the local circular speed. We also show that these gradients are incompatible with accretion occurring at the edge of the discs and flowing radially inward. Finally, we investigate gas accretion from a hot corona with a cosmological angular momentum distribution and describe how simple models of rotating coronae guarantee the inside-out growth of disc galaxies.

scholarly journals Identification of dusty massive stars in star-forming dwarf irregular galaxies in the Local Group with mid-IR photometry

2015 ◽  
Vol 584 ◽  
pp. A33 ◽  
Author(s):  
N. E. Britavskiy ◽  
A. Z. Bonanos ◽  
A. Mehner ◽  
M. L. Boyer ◽  
K. B. W. McQuinn
Keyword(s):  
Local Group ◽  
Massive Stars ◽  
Star Forming ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies ◽  
Ir Photometry

scholarly journals Magnetic fields in dwarfs versus early-type galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 454-455
Author(s):  
Krzysztof T. Chyży
Keyword(s):  
Magnetic Fields ◽  
Formation Rate ◽  
Mean Value ◽  
Early Type ◽  
Star Forming ◽  
Spiral Density Waves ◽  
Irregular Galaxies ◽  
Effective Generation ◽  
The Mean ◽  
Dwarf Irregular Galaxies

AbstractAccording to a recent systematic study of dwarf irregular galaxies the production of their magnetic fields appears to be regulated mainly by the surface density of the galactic star-formation rate. Magnetic fields in nearby dwarfs are typically weak, with the mean value of the total field strength three times smaller than in the normal spirals. Dwarfs with stronger fields reveal vivid star-forming activity, have clear signs of current or recent gravitational interactions, are more massive and evolved systems. Recently discovered strong regular fields in an early-type ringed galaxy NGC 4736 also indicates that even without spiral density waves an effective generation of strong magnetic fields is possible in any type of galaxy if only starburst characteristics are reached.

scholarly journals OUTSIDE-IN SHRINKING OF THE STAR-FORMING DISK OF DWARF IRREGULAR GALAXIES

2012 ◽  
Vol 143 (2) ◽  
pp. 47 ◽  
Author(s):  
Hong-Xin Zhang ◽  
Deidre A. Hunter ◽  
Bruce G. Elmegreen ◽  
Yu Gao ◽  
Andreas Schruba
Keyword(s):  
Star Forming ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

scholarly journals Infrared Properties of Star-forming Dwarf Galaxies. I. Dwarf Irregular Galaxies in the Local Volume

2005 ◽  
Vol 130 (4) ◽  
pp. 1593-1626 ◽  
Author(s):  
Ovidiu Vaduvescu ◽  
Marshall L. McCall ◽  
Michael G. Richer ◽  
Robin L. Fingerhut
Keyword(s):  
Dwarf Galaxies ◽  
Star Forming ◽  
Local Volume ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

scholarly journals Morphological aspects of star formation in dwarf galaxies

1999 ◽  
Vol 171 ◽  
pp. 261-270
Author(s):  
Noah Brosch ◽  
Ana Heller ◽  
Elchanan Almoznino
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
High Surface ◽  
Dark Matter Halo ◽  
Star Forming ◽  
Star Forming Regions ◽  
Tidal Interactions ◽  
Irregular Galaxies ◽  
Asymmetric Pattern ◽  
Dwarf Irregular Galaxies

AbstractWe studied the morphology of star formation in dwarf irregular galaxies and found that, in general, this takes place on one side of a galaxy and far from the center. This is mainly true for low surface brightness galaxies; in high surface brightness dwarf irregulars the star formation tends to be more centrally concentrated, as well as being more intense. We discuss possible star formation triggers in dwarf irregular galaxies, and evaluate the reasons for the peculiar distribution of star forming regions of these galaxies. Stochastic star formation, interactions with external gas, and tidal interactions appear to be ruled out as responsible for the asymmetric pattern of star formation. We conclude that asymmetry of a dark matter halo or of an asymmetric underlying stellar distribution may trigger an asymmetric pattern of star formation.

scholarly journals The SED of the nearby H i-massive LIRG HIZOA J0836–43: from the NIR to the radio domain

2011 ◽  
Vol 7 (S284) ◽  
pp. 213-217
Author(s):  
Renée C. Kraan-Korteweg ◽  
Michelle E. Cluver
Keyword(s):  
Star Formation ◽  
Line Emission ◽  
Infrared Emission ◽  
Optical Data ◽  
Stellar Disk ◽  
Massive Galaxies ◽  
Star Forming ◽  
Mir Spectroscopy ◽  
The Galaxy ◽  
Multi Wavelength

AbstractHIZOA J0836–43 is one of the most H i-massive galaxies in the local (z < 0.1) Universe. Not only are such galaxies extremely rare, but this “coelacanth” galaxy exhibits characteristics – in particular its active, inside-out stellar disk-building – that appear more typical of past (z ~ 1) star formation, when large gas fractions were more common. Unlike most local giant H i galaxies, it is actively star forming. Moreover, the strong infrared emission is not induced by a merger event or AGN, as is commonly found in other local LIRGs. The galaxy is suggestive of a scaled-up version of local spiral galaxies; its extended star formation activity likely being fueled by its large gas reservoir and, as such, can aid our understanding of star formation in systems expected to dominate at higher redshifts. The multi-wavelength imaging and spectroscopic observations that have led to these deductions will be presented. These include NIR (JHK) and MIR (Spitzer; 3 – 24μm) imaging and photometry, MIR spectroscopy, ATCA H i-interferometry and Mopra CO line emission observations. But no optical data, as the galaxy is heavily obscured due to its location in Vela behind the Milky Way.

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