Star formation and abundances in the nearby irregular galaxy VII ZW 403

Tully, R. Brent; Boesgaard, Ann Merchant; Dyck, H. M.; Schempp, W. V.

doi:10.1086/158896

Cited by 26 publications

(21 citation statements)

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“…Although Tully et al (1981) proposed that the galaxy might be a member of the M81 Group, more recent distance determinations (Lynds et al 1998) locate it about 1.5 Mpc farther away at 4.5 Mpc distance. Therefore, it can be considered an isolated galaxy (Schulte-Ladbeck et al 1999).…”

Section: The Main Observational Properties Of VII Zw 403mentioning

confidence: 95%

On the Recent History of Star Formation in the Blue Compact Dwarf Galaxy VII Z[CLC]w[/CLC] 403

Silich

Tenorio-Tagle

Muñoz–Tuñón

et al. 2002

The Astronomical Journal

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Here we attempt to infer the recent history of star formation in the BCD galaxy VII Zw 403, based on an analysis that accounts for the dynamics of the remnant generated either by an instantaneous burst or by a continuous star formation event. The models are restricted by the size of the diffuse X-ray-emitting region, the H luminosity from the star-forming region, and the superbubble diffuse X-ray luminosity. We have reobserved VII Zw 403 with a better sensitivity corresponding to the threshold H flux 8:15 Â 10 À17 ergs cm À2 s À1 . The total H luminosity derived from our data is much larger than reported before and presents a variety of ionized filaments and incomplete shells superimposed on the diffuse H emission. This result has a profound impact on the predicted properties of the starburst-blown superbubble. Numerical calculations based on the Hubble Space Telescope H data predict two different scenarios of star formation able to match simultaneously all observed parameters. These are an instantaneous burst of star formation with a total mass of 5 Â 10 5 M and a star-forming event with a constant star formation rate SFR ¼ 4 Â 10 À3 M yr À1 , which lasts for 35 Myr. The numerical calculations based on the energy input rate derived from our observations predict a short episode of star formation lasting less than 10 Myr with a total star cluster mass of $ð1 3Þ Â 10 6 M . However, the five main star-forming knots are sufficiently distant to form a coherent shell in a short timescale and still keep their energies blocked within local, spatially separated bubbles. The X-ray luminosities of these are here shown to be consistent with the ROSAT PSPC diffuse X-ray emission.

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Section: The Main Observational Properties Of VII Zw 403mentioning

confidence: 95%

On the Recent History of Star Formation in the Blue Compact Dwarf Galaxy VII Z[CLC]w[/CLC] 403

Silich

Tenorio-Tagle

Muñoz–Tuñón

et al. 2002

The Astronomical Journal

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“…179,312,349,377), but the nature of this older population and the number of previous generations of stars are not so clear. In the dwarf Irr VII Zw 403, for example, the metallicity of the gas is sufficiently low and the level of current star formation sufficiently vigorous that one is forced to doubt whether the galaxy could have formed stars in this vigorous way at an earlier stage (361). Nevertheless, the existence of a diffuse stellar component implies that an older popUlation is in fact present.…”

Section: Stellar Populationsmentioning

confidence: 99%

“…This may be indicative of preferential selection of galaxies qurently experiencing major star-forming events in samples of intrinsically small, faint galaxies. An example of the importance of star fo rmation on the detectability of dwarf Irrs can be fo und by comparing VII Zw 403, a high surface brightness Local Group dwarf (361), with the low surface brightness Local Group Irr LSG 3 (363) ; the differences between these two galaxies stem from the presence of a small 0 B stellar complex in VII Zw 403. Unlike spirals, Irrs often show a central bluing of optical color (81,83).…”

Section: Introductionmentioning

confidence: 99%

“…abundances of 0, Ne, and N; for a review, see 268) have been determined fr om the emission-line ratios under the assumption of photo ionization (4, 30) for a large number of high surface brightness Ins (120, 191, 209, 216a, 226, 340, 381) and low surface brightness, dwarf Irrs (cf. 189,226,267,270,329,340,361). The abundances generally range from SMC-like to LMC-like, with no distinction between the high and low surface brightness systems.…”

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Structure and Evolution of Irregular Galaxies

Gallagher¹,

Hunter²

1984

Annu. Rev. Astron. Astrophys.

116

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INTRODUCTIONIrregular galaxies (Irrs) usually are smaller, less massive, and optically dimmer than commonly studied giant spirals, SOs, and classical ellipticals. At first giance they also appear to be rare objects that make up only a few percent of the major bright galaxy catalogs (87, 300). Is there then much reward in pursuing such faint and elusive galaxies? The answer to this question turns out to be a surprisingly strong "yes." An examination of more nearly complete samples of galaxies (213,341,366) reveals that Irrs account for it substantial (1/3-1/2) fraction of all galaxies, and that they certainly are dominant by number density among actively star-forming galaxies. A diversity of nearby examples therefore abound [including, of course, the Large and Small Magellanic Clouds (LMC and SMC)], making Irrs prime targets for detailed investigations of galactic stellar content and star fo rmation processes. Recognition of their structural simplicity has provided an additional stimulus for recent interest in Irrs as tests for theories of galaxy structure and evolution. These galaxies also are comparatively unevolved; and thus they may yield further rewards by allowing conditions to be defined in the poorly understood realm of low density extragalactic systems, which retain considerable information about galaxy formation (101, 327).In the broadest sense, the irregular galaxy class is loosely defined (e.g. see illustrations in 9, 23, 378,379). Hubble (175, 176) originally bu�lt on earlier nebular classification schemes (e.g. 153) and considered galaxies to be "irregular" if they showed chaotic, non symmetrical blue-light distributions, in contrast with the axial symmetry of normal "regular" systems. Later classification systems subdivide irregular galaxies into tWb major groups : Magellanic systems (Irr I, 1m), which resemble the Magellanic Clouds; and peculiar, often amorphous galaxies, which are classified as Irr II or 10 systems (72,174,290,292).Unfortunately, irregular structures may arise from a vari�ty of physical causes, and as a result a wide range of physical types of irregular galaxies are known to exist : (a) There may be substantial chaos in the projected stellar mass distributions in galaxies, although such nonequilibrium structures are unlikely to survive for more than a fe w rotation periods ("" 109 yr). Most currently kilOwn galaxies in disturbed states seem to be involved in galaxy galaxy intetactions (3 11, 358, 359, 384, 392, 393), although newly fo rmed galaxies could also find themselves in this situation (45). Some galaxies classified as Irr II or IO also belong in the category of interacting galaxies. (b) Similarly, unusual distributions of dense interstellar gas across the face of a galaxy may produce an optical image that is mottled by dark lanes. The dusty Irr II galaxies discussed by Krienke & Hodge (214) belong in this group. As these authors note, extended interstellar matter also can lead to emission filaments and reflection nebulae on galactic scales that give rise to abnormal optica...

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“…Hunter & Elmegreen (2004) found that the closest galaxy to VII Zw 403 within ±150 km s 1 is KDG 073 at a distance of 900 kpc and a velocity difference of 32 km s 1 . VII Zw 403's H I has been studied using the GBT, Nançay, the GMRT, and the VLA (Tully et al 1981;Paturel et al 2003;Begum et al 2008;Roychowdhury et al 2009;Thuan et al 2004;. The H I data reveal a galaxy that has a disturbed velocity field and irregular morphology.…”

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confidence: 99%

The HI Chronicles of LITTLE THINGS Blue Compact Dwarf Galaxies

Ashley¹

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Star formation and abundances in the nearby irregular galaxy VII ZW 403

Cited by 26 publications

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On the Recent History of Star Formation in the Blue Compact Dwarf Galaxy VII Z[CLC]w[/CLC] 403

On the Recent History of Star Formation in the Blue Compact Dwarf Galaxy VII Z[CLC]w[/CLC] 403

Structure and Evolution of Irregular Galaxies

The HI Chronicles of LITTLE THINGS Blue Compact Dwarf Galaxies

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