High resolution fabry-perot and multi-pupil spectral observations of the genuine blue compact dwarf galaxy IZW18

Петросян, А. Р.; Comte, G.; Boulesteix, J.; Kunth, D.; Movsessian, T. A.; Додонов, С. Н.; Coarer, E. Le; Буренков, А. Н.

doi:10.1007/bf02044707

Cited by 27 publications

(48 citation statements)

References 20 publications

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“…9, white contours). Moreover, the Hα velocity field of Petrosian et al (1997) shows a gradient along the arc similar to the one observed in Fig. 2 (middle-right), confirming the physical association between H i and Hα.…”

Section: The Connection Between the H I And Hα Emissionsupporting

confidence: 77%

“…This feature was first identified by Dufour & Hester (1990) and interpreted as a radiation-bound ionization front driven into the ISM. Petrosian et al (1997), instead, argued that the Hα arc also contains stellar emission and suggested that it is a structure with stars that are able to ionize the gas "in situ". The H i to the west of I Zw 18 A is associated with the Hα arc.…”

Section: The Connection Between the H I And Hα Emissionmentioning

confidence: 99%

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Dynamics of starbursting dwarf galaxies: I Zw 18

Lelli

Verheijen

Fraternali

et al. 2012

A&A

124

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I Zw 18 is a prototype blue compact dwarf (BCD) galaxy, characterized by a strong starburst and extremely low metallicity (Z ∼ 0.02 Z ). It has long been considered a candidate young galaxy in the Local Universe, but recent studies have found that it contains old stars. We analysed archival VLA observations of the 21 cm line and found that the H i associated to the starburst region forms a compact rapidly rotating disk. The H i column densities are very high, up to ∼50-100 M pc −2 (∼0.6−1.2 × 10 22 atoms cm −2 ). The rotation curve is flat with a steep rise in the inner parts, indicating that there is a strong central concentration of mass. Mass models with a dark matter halo show that baryons may dominate the gravitational potential in the inner regions. A radial inflow/outflow motion of ∼15 km s −1 is also present. I Zw 18 appears to be structurally different from typical dwarf irregulars in terms of its gas distribution, stellar distribution, and dynamics. It may be considered as a "miniature" high-surface-brightness disk galaxy. These dynamical properties must be tightly related to the starburst. They also shed new light on the question of the descendants of BCDs. There is also extended H i emission towards the outlying stellar complex I Zw 18 C and a ∼13.5 kpc H i tail. An interaction/merger between gas-rich dwarfs is the most likely explanation of the starburst.

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Section: The Connection Between the H I And Hα Emissionsupporting

confidence: 77%

Section: The Connection Between the H I And Hα Emissionmentioning

confidence: 99%

Dynamics of starbursting dwarf galaxies: I Zw 18

Lelli

Verheijen

Fraternali

et al. 2012

A&A

124

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“…Lequeux & Viallefond 1980;Davidson & Kinman 1985;Viallefond et al 1987;Petrosian et al 1997;van Zee et al 1998). The H i column density is as high as N H i 2 × 10 21 cm −2 (Vidal-Madjar et al 2000).…”

Section: Izw18mentioning

confidence: 97%

Multiple starbursts in Blue Compact Galaxies

Recchi

Matteuccí

D’Ercole

et al. 2002

A&A

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Abstract. In this paper we present some results concerning the effects of two instantaneous starbursts, separated by a quiescent period, on the dynamical and chemical evolution of Blue Compact Dwarf galaxies. In particular, we compare the model results to the galaxy IZw18, which is a very metal-poor, gas-rich dwarf galaxy, possibly experiencing its first or second burst of star formation. We follow the evolution of a first weak burst of star formation followed by a second more intense one occurring after several hundred million years. We find that a galactic wind develops only during the second burst and that metals produced in the burst are preferentially lost, relative to the hydrogen gas. We predict the evolution of several chemical abundances (H, He, C, N, O, α-elements, Fe) in the gas inside and outside the galaxy, by taking into account, in detail, the chemical and energetical contributions from type II and Ia supernovae. We find that the abundances predicted for the star forming region are in good agreement with the H ii region abundances derived for IZw18. We also predict the abundances of C, N and O expected for the H i gas to be compared with future FUSE abundance determinations. We conclude that IZw18 must have experienced two bursts of star formation, one occurred ∼300 Myr ago and a recent one with an age between 4-7 Myr. However, by taking into account also other independent estimates, such as the color-magnitude diagram and the spectral energy distribution of stars in IZw18, and the fact that real starbursts are not instantaneous, we suggest that it is more likely that the burst age is between 4 and 15 Myr.

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“…For this, we calculate the mass of each element in the H  region locked in dust that would be required to explain the observed abundance discontinuity between the H  and the H  region. Given the small mass fraction of ionized gas in I Zw 18 (e.g., Petrosian et al 1997), we expect most of the dust mass to lie in the H  region and we therefore ignore the depletion in the H  region. Dust extinction toward I Zw 18 is mostly Galactic, and the dust mass in I Zw 18 is exceptionally low.…”

Section: Depletion On Dust Grainsmentioning

confidence: 99%

Chemical enrichment and physical conditions in I Zw 18

Lebouteiller

Heap

Hubený

et al. 2013

A&A

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Context. Low-metallicity star-forming dwarf galaxies are prime targets to understand the chemical enrichment of the interstellar medium. The H  region contains the bulk of the mass in blue compact dwarfs, and it provides important constraints on the dispersal and mixing of heavy elements released by successive star-formation episodes. The metallicity of the H  region is also a critical parameter to investigate the future star-formation history, as metals provide most of the gas cooling that will facilitate and sustain star formation. Aims. Our primary objective is to study the enrichment of the H  region and the interplay between star-formation history and metallicity evolution. Our secondary objective is to constrain the spatial-and time-scales over which the H  and H  regions are enriched, and the mass range of stars responsible for the heavy element production. Finally, we aim to examine the gas heating and cooling mechanisms in the H  region. Methods. We observed the most metal-poor star-forming galaxy in the Local Universe, I Zw 18, with the Cosmic Origin Spectrograph onboard Hubble. The abundances in the neutral gas are derived from far-ultraviolet absorption-lines (H , C , C *, N , O , ...) and are compared to the abundances in the H  region. Models are constructed to calculate the ionization structure and the thermal processes. We investigate the gas cooling in the H  region through physical diagnostics drawn from the fine-structure level of C + . Results. We find that H  region abundances are lower by a factor of ∼2 as compared to the H  region. There is no differential depletion on dust between the H  and H  region. Using sulfur as a metallicity tracer, we calculate a metallicity of 1/46 Z (vs. 1/31 Z in the H  region). From the study of the C/O, [O/Fe], and N/O abundance ratios, we propose that C, N, O, and Fe are mainly produced in massive stars. We argue that the H  envelope may contain pockets of pristine gas with a metallicity essentially null. Finally, we derive the physical conditions in the H  region by investigating the C * absorption line. The cooling rate derived from C * is consistent with collisions with H 0 atoms in the diffuse neutral gas. We calculate the star-formation rate from the C * cooling rate assuming that photoelectric effect on dust is the dominant gas heating mechanism. Our determination is in good agreement with the values in the literature if we assume a low dust-to-gas ratio (∼2000 times lower than the Milky Way value).

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High resolution fabry-perot and multi-pupil spectral observations of the genuine blue compact dwarf galaxy IZW18

Cited by 27 publications

References 20 publications

Dynamics of starbursting dwarf galaxies: I Zw 18

Dynamics of starbursting dwarf galaxies: I Zw 18

Multiple starbursts in Blue Compact Galaxies

Chemical enrichment and physical conditions in I Zw 18

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