scholarly journals Haro15: Is it actually a low metallicity galaxy?

2009 ◽  
Vol 5 (S265) ◽  
pp. 243-244
Author(s):  
Verónica Firpo ◽  
Guillermo Bosch ◽  
Guillermo Hägele ◽  
Ángeles I. Díaz ◽  
Nidia Morrell
Keyword(s):  
Dwarf Galaxy ◽  
Empirical Methods ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Ionization Structure ◽  
The Galaxy ◽  
Low Metallicity ◽  
Echelle Spectroscopy ◽  
Abundance Determination ◽  
Blue Compact Dwarf Galaxy

AbstractWe present a detailed study of the physical properties of the nebular material in multiple knots of the blue compact dwarf galaxy Haro 15. Using long slit and echelle spectroscopy, obtained at Las Campanas Observatory, we study the physical conditions (electron density and temperature), ionic and total chemical abundances of several atoms, reddening and ionization structure. The latter was derived by comparing the oxygen and sulphur ionic ratios to their corresponding observed emission line ratios (the η and η' plots) in different regions of the galaxy. Applying direct and empirical methods for abundance determination, we perform a comparative analysis between these regions.

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 The Dark Blue Compact Dwarf Galaxy NGC 2915

1997 ◽  
Vol 14 (1) ◽  
pp. 77-80 ◽  
Author(s):  
Gerhardt R. Meurer
Keyword(s):  
Dark Matter ◽  
Mass Distribution ◽  
Dwarf Galaxy ◽  
Dark Matter Halo ◽  
High Mass ◽  
Mass Star ◽  
Normal Galaxies ◽  
The Galaxy ◽  
Dark Blue ◽  
Blue Compact Dwarf Galaxy

AbstractRecent results on NGC 2915, the first blue compact dwarf galaxy to have its mass distribution modelled, are summarised. NGC 2915 is shown to have HI well beyond its detected optical extent. Its rotation curve is well determined and fit with maximum disk mass models. The dark matter halo dominates the mass distribution at nearly all radii, and has a very dense core compared to those of normal galaxies. High-mass star formation energises the HI in the centre of the galaxy, but appears to be maintained in viriai equilibrium with the dark matter halo. The implications of these results are briefly discussed.

scholarly journals Multiwavelength Observations of the Low-Metallicity Blue Compact Dwarf Galaxy SBS 0335−052

2001 ◽  
Vol 122 (4) ◽  
pp. 1736-1746 ◽  
Author(s):  
Daniel A. Dale ◽  
George Helou ◽  
Gerry Neugebauer ◽  
B. T. Soifer ◽  
David T. Frayer ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Low Metallicity ◽  
Blue Compact Dwarf Galaxy ◽  
Multiwavelength Observations

scholarly journals Nearby Blue Compact Dwarf Galaxy NGC 6789

1999 ◽  
Vol 192 ◽  
pp. 253-258
Author(s):  
I. Drozdovsky ◽  
N. Tikhonov
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
High Surface ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Metal Abundance ◽  
The Mean ◽  
Red Giant ◽  
Halo Population ◽  
Blue Compact Dwarf Galaxy

We present the results of a detailed BVRI and Hα study of the isolated nearby blue compact dwarf (BCD) galaxy NGC 6789. Judging from the literature the observed galaxy has not yet been resolved into stars up to now. On CCD frames obtained with 6m BTA telescope and 2.5m Nordic telescope the galaxy is well resolved. Its colour-magnitude diagram confirms the two component (core-halo) galaxy morphology, which consists of two stellar populations distinct in structure and colour: an inner high surface-brightness young population within 150 pc from the center of the galaxy, and a relatively low surface-brightness intermediate-age population extending out to at least 600 pc. The distance to the galaxy, estimated from the tip of the red giant branch (TRGB) is 2.1 Mpc which places NGC 6789 close to the Local Group. From the mean colour of the RGB, the mean metal abundance of the halo population is estimated as [Fe/H] ≃ −1 dex.

scholarly journals VLT/FORS Surveys of Wolf-Rayet Stars in the Nearby Universe

2007 ◽  
Vol 3 (S250) ◽  
pp. 327-332
Author(s):  
Lucy J. Hadfield ◽  
Paul A. Crowther
Keyword(s):  
Local Group ◽  
Narrow Band ◽  
Dwarf Galaxy ◽  
Narrow Band Imaging ◽  
Interstellar Extinction ◽  
Spectroscopic Studies ◽  
Order Of Magnitude ◽  
Low Metallicity ◽  
Massive Clusters ◽  
Blue Compact Dwarf Galaxy

AbstractWe present results from a series of VLT/FORS narrow-band imaging and spectroscopic surveys of Wolf-Rayet (WR) stars in nearby spiral galaxies and compare observed populations in high- and low metallicity environments. The metal-rich galaxy M 83 is seen to host an exceptional WR content, with over 1000 WR stars being detected. N(WC)/N(WN) ~ 1.2 and late-type WC subtypes dominate the WC population. At low metallicity, ~100 stars has been identified within NGC 1313, with N(WC)/N(WN) ~ 0.5. In contrast to M83, the WC population of NGC 1313 comprises solely early subtypes plus a WO star (the first WO star to be identified beyond the Local Group). Consequently, the dominant WC subtype may serve as a crude metallicity diagnostic for WR galaxies.In addition, the WR content of the blue compact dwarf galaxy NGC 3125 is examined. Previous UV and optical spectroscopic studies of knot A in NGC 3125 derive WR populations which differ by more than an order of magnitude. New VLT observations and archival HST spectroscopy reconcile this discrepancy via the use of LMC WR spectral templates and a reduced nebular-derived interstellar extinction. Empirical N(WR)/N(O) ratios for clusters within NGC 3125 are a factor of two higher than evolutionary synthesis predictions but are consistent with those observed for other young massive clusters.

scholarly journals Ionized and neutral gas in the XUV discs of nearby spiral galaxies

2014 ◽  
Vol 10 (S309) ◽  
pp. 65-68
Author(s):  
López-Sánchez ◽  
B. S. Koribalski ◽  
T. Westmeier ◽  
C. Esteban
Keyword(s):  
Spiral Galaxies ◽  
Dwarf Galaxy ◽  
Chemical Abundances ◽  
Ionized Gas ◽  
Galaxy Interactions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Neutral Gas ◽  
The Galaxy ◽  
Nearby Galaxies

AbstractWe are conducting a multiwavelength study of XUV discs in nearby, gas-rich spiral galaxies combining the available UV (GALEX) observations with H i data obtained at the ATCA as part of the Local Volume HI Survey (LVHIS) project and multi-object fibre spectroscopy obtained using the 2dF/AAOmega instrument at the 3.9m AAT. Here we present the results of the multiwavelength analysis of the galaxy pair NGC 1512/1510. The H i distribution of NGC 1512 is very extended with two pronounced spiral/tidal arms. Hundreds of independent UV-bright regions are associated with dense H i clouds in the galaxy outskirts. We confirm the detection of ionized gas in the majority of them and characterize their physical properties, chemical abundances and kinematics. Both the gas distribution andthe distribution of the star-forming regions are affected by gravitational interactionwith the neighbouring blue compact dwarf galaxy NGC 1510. Our multiwavelength analysis provides new clues about local star-formation processes, the metal redistribution in the outer gaseous discs of spiral galaxies, the importance of galaxy interactions, the fate of the neutral gas and the chemical evolution in nearby galaxies.

scholarly journals [TSUP]12[/TSUP]CO Mapping of the Low-Metallicity Blue Compact Dwarf Galaxy Markarian 86

2002 ◽  
Vol 573 (2) ◽  
pp. L101-L105 ◽  
Author(s):  
A. Gil de Paz ◽  
S. A. Silich ◽  
B. F. Madore ◽  
C. Sánchez Contreras ◽  
J. Zamorano ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Low Metallicity ◽  
Blue Compact Dwarf Galaxy
Sign in / Sign up

Export Citation Format

Share Document