scholarly journals Booms and Busts: the Burstiness of Star Formation in Nearby Dwarf Galaxies

2010 ◽  
Vol 27 (3) ◽  
pp. 234-241 ◽  
Author(s):  
A. A. Cole
Keyword(s):  
Galaxy Evolution ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Starburst Galaxy ◽  
Ic 10 ◽  
Irregular Galaxies ◽  
Magnitude Diagram ◽  
Nearby Galaxies ◽  
Dwarf Irregular Galaxies ◽  
The Universe

AbstractIn this review I summarise recent advances in our understanding of the importance of starburst events to the evolutionary histories of nearby galaxies. Ongoing bursts are easily diagnosed in emission-line surveys, but assessing the timing and intensity of fossil bursts requires more effort, usually demanding color–magnitude diagrams or spectroscopy of individual stars. For ages older than ∼1 Gyr, this type of observation is currently limited to the Local Group and its immediate surroundings. However, if the Local Volume is representative of the Universe as a whole, then studies of the age and metallicity distributions of star clusters and resolved stellar populations should give statistical clues as to the frequency and importance of bursts to the histories of galaxies in general. Based on starburst statistics in the literature and synthetic colour-magnitude diagram studies of Local Group galaxies, I attempt to distinguish between systemic starbursts that strongly impact galaxy evolution and stochastic bursts that can appear impressive but are ultimately of little significance on gigayear timescales. As a specific case, it appears as though IC 10, the only starburst galaxy in the Local Group, falls into the latter category and is not fundamentally different from other nearby dwarf irregular galaxies.

scholarly journals Planetary Nebulae as a Probe of the Local Group Galaxies Evolution

2006 ◽  
Vol 2 (S235) ◽  
pp. 215-215
Author(s):  
A. Y. Kniazev ◽  
S. A. Pustilnik ◽  
E. K. Grebel ◽  
D. B. Zucker ◽  
P. Vaisanen
Keyword(s):  
Local Group ◽  
Planetary Nebulae ◽  
Ic 10 ◽  
Irregular Galaxies ◽  
Ngc 6822 ◽  
Dwarf Irregular Galaxies

AbstractWe present the latest results from our study of PNe and HII regions in two Local Group dwarf irregular galaxies IC 10 and NGC 6822.

scholarly journals Luminous Infrared Sources in the Local Group: Identifying the Missing Links in Massive Star Evolution

2014 ◽  
Vol 9 (S307) ◽  
pp. 92-93
Author(s):  
N. Britavskiy ◽  
A. Z. Bonanos ◽  
A. Mehner
Keyword(s):  
Massive Star ◽  
Local Group ◽  
Massive Stars ◽  
Star Evolution ◽  
Irregular Galaxies ◽  
Nearby Galaxies ◽  
Massive Star Evolution ◽  
Infrared Sources ◽  
Dwarf Irregular Galaxies

AbstractWe present the first systematic survey of dusty massive stars (RSGs, LBVs, sgB[e]) in nearby galaxies, with the goal of understanding their importance in massive star evolution. Using the fact that these stars are bright in mid-infrared colors due to dust, we provide a technique for selecting and identifying dusty evolved stars based on the results of Bonanos et al. (2009, 2010), Britavskiy et al. (2014), and archival Spitzer/IRAC photometry. We present the results of our spectroscopic follow-up of luminous infrared sources in the Local Group dwarf irregular galaxies: Pegasus, Phoenix, Sextans A and WLM. The survey aims to complete the census of dusty massive stars in the Local Group.

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 Physical parameters of red supergiants in dwarf irregular galaxies in the Local Group

2019 ◽  
Vol 631 ◽  
pp. A95 ◽  
Author(s):  
N. E. Britavskiy ◽  
A. Z. Bonanos ◽  
A. Herrero ◽  
M. Cerviño ◽  
D. García-Álvarez ◽  
...  
Keyword(s):  
Local Group ◽  
Massive Stars ◽  
Physical Parameters ◽  
Agb Stars ◽  
Ic 10 ◽  
Irregular Galaxies ◽  
Red Supergiants ◽  
Effective Temperatures ◽  
Dwarf Irregular Galaxies ◽  
Fundamental Physical

Context. Increasing the statistics of evolved massive stars in the Local Group enables investigating their evolution at different metallicities. During the late stages of stellar evolution, the physics of some phenomena, such as episodic and systematic mass loss, are not well constrained. For example, the physical properties of red supergiants (RSGs) in different metallicity regimes remain poorly understood. Thus, we initiated a systematic study of RSGs in dwarf irregular galaxies (dIrrs) in the Local Group. Aims. We aim to derive the fundamental physical parameters of RSGs and characterize the RSG population in nearby dIrrs. Methods. The target selection is based on 3.6 μm and 4.5 μm photometry from archival Spitzer Space Telescope images of nearby galaxies. We selected 46 targets in the dIrrs IC 10, IC 1613, Sextans B, and the Wolf-Lundmark-Melotte (WLM) galaxy that we observed with the GTC–OSIRIS and VLT–FORS2 instruments. We used several photometric techniques together with a spectral energy distribution analysis to derive the luminosities and effective temperatures of known and newly discovered RSGs. Results. We identified and spectroscopically confirmed 4 new RSGs, 5 previously known RSGs, and 5 massive asymptotic giant branch (AGB) stars. We added known objects from previous observations. In total, we present spectral classification and fundamental physical parameters of 25 late-type massive stars in the following dIrrs: Sextans A, Sextans B, IC 10, IC 1613, Pegasus, Phoenix, and WLM. This includes 17 RSGs and 8 AGB stars that have been identified here and previously. Conclusions. Based on our observational results and PARSEC evolutionary models, we draw the following conclusions: (i) a trend to higher minimum effective temperatures at lower metallicities and (ii) the maximum luminosity of RSGs appears to be constant at log(L/L⊙)≈5.5, independent of the metallicity of the host environment (up to [Fe/H] ≈ −1 dex).

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 The Motion of the Local Group of Galaxies with Respect to the Background of Galaxies

1983 ◽  
Vol 104 ◽  
pp. 255-258
Author(s):  
R. D. Davies
Keyword(s):  
Large Scale ◽  
Local Group ◽  
Microwave Background ◽  
Optical Studies ◽  
Group Motion ◽  
Gravitational Influence ◽  
Nearby Galaxies ◽  
Peculiar Motion ◽  
The Universe ◽  
Hubble Flow

A measurement of the motion of the Local Group of galaxies through the Universe provides an indication of their peculiar motion relative to the Hubble flow consequent upon the gravitational influence of the local large scale mass inhomogeneities. This motion can be measured either relative to the cosmic microwave background at z ∼ 1000 or relative to the background or nearby (z ∼ 0.01) galaxies. The interpretation of published measurements is subject to some uncertainty. As an example, the Local Group motion derived from optical studies of nearby galaxies (Rubin et al. 1976) differs from that derived from radio frequency measurements of the dipole anisotropy in the microwave background. (Boughn et al. 1981, Gorenstein & Smoot 1981).

scholarly journals Chemical abundances of massive stars in Local Group galaxies

2003 ◽  
Vol 212 ◽  
pp. 30-37 ◽  
Author(s):  
Kim A. Venn ◽  
Andreas Kaufer ◽  
Eline Tolstoy ◽  
Rolf-Peter Kudritzki ◽  
Norbert Przybilla ◽  
...  
Keyword(s):  
High Efficiency ◽  
Local Group ◽  
Iron Group ◽  
Chemical Abundances ◽  
Elemental Abundances ◽  
Irregular Galaxies ◽  
Ngc 6822 ◽  
Process Elements ◽  
Star Formation Histories ◽  
Dwarf Irregular Galaxies

The relative abundances of elements in galaxies can provide valuable information on the stellar and chemical evolution of a galaxy. While nebulae can provide abundances for a variety of light elements, stars are the only way to directly determine the abundances of iron-group and s-process and r-process elements in a galaxy. The new 8m and 10m class telescopes and high-efficiency spectrographs now make high-quality spectral observations of bright supergiants possible in dwarf galaxies in the Local Group. We have been concentrating on elemental abundances in the metal-poor dwarf irregular galaxies, NGC 6822, WLM, Sextants A, and GR 8. Comparing abundance ratios to those predicted from their star formation histories, determined from color-magnitude diagrams, and comparing those ratios between these galaxies can give us new insights into the evolution of these dwarf irregular galaxies. Iron-group abundances also allow us to examine the metallicities of the stars in these galaxies directly, which affects their inferred mass loss rates and predicted stellar evolution properties.

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