The O/H Distribution in the Low-Mass Galaxies NGC 2366 and NGC 4395

Roy, Jean-René; Belley, Julien; Dutil, Yvan; Martin, Pierre

doi:10.1086/176968

Cited by 49 publications

(31 citation statements)

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“…Across a given BCDG, the spatial scale-length is supposed to be sufficiently small (of the order of a kiloparsec or even much smaller) for abundance fluctuations to be probably not detectable using the sole [OIII]/Hβ ratio as indicator, the accuracy of its calibration versus log[O/H] being not better than ±0.2 dex (see e.g. Edmunds & Pagel 1984;Zaritsky 1992;Roy et al 1996). Moreover, classical HII region models show that, for a given abundance, the dilution factor of the ionized gas has an important influence on the computed excitation ratio (see e.g.…”

Section: Emission Lines and Continuum Mapsmentioning

confidence: 99%

Multi-wavelength study of a new sample of blue compact dwarf galaxies

Петросян¹,

Movsessian²,

Comte³

et al. 2002

A&A

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Abstract. We present the multi-pupil integral field spectroscopy of 18 Blue Compact Dwarf Galaxies performed at the 6 m telescope of the SAO (Russia). We produce an atlas of the Hα, [OIII], [SII] emission-line intensity distributions, the excitation parameter ([OIII]/Hβ ratio), the continuum maps in blue and red and the velocity fields as derived from the 2D spectra. We provide detailed individual descriptions of the objects with a table of their spectroscopic properties. From the atlas and the velocity maps, we have classified the sample according to the following scheme: -Nine objects show spatially coincident distributions with respect to their emission lines, excitation parameter and the continuum. In this case, these galaxies are repeating star-formation sequences at the same spatial location. Mrk 1416 also belongs to this class of BCDG but has a secondary site of star formation. -Eight objects in which the distributions in emission lines brightness, excitation parameter and in continuum strength differ from each other at various degrees. These objects are galaxies with several sites of star formation of various ages and spatial locations. They can be ideal templates for testing the models of star formation.-From the 2-D [SII] emission-line distribution we find a superbubble structure in one object and possibly in 2 others. -Ten objects show an overall quite regular radial velocity gradient. On the other hand, in 8 objects, the kinematical major axis of this regular velocity field does not align with the photometric major axis, suggesting dynamical disturbances, gas/star decoupling and/or instabilities. -Six objects have irregular velocity fields, implying that the rotation of a gaseous disk is not their dominant dynamical signature. -SBS 1723+565B is not a dwarf galaxy but a giant irregular galaxy or an interacting system experiencing a high star formation rate.

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Section: Emission Lines and Continuum Mapsmentioning

confidence: 99%

Multi-wavelength study of a new sample of blue compact dwarf galaxies

Петросян¹,

Movsessian²,

Comte³

et al. 2002

A&A

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“…There are other H ii regions in NGC 2366 in addition to NGC 2363. Roy et al (1996) have derived the abundances for several of these H ii regions. They find their oxygen abundances 12 þ log O/ H to be in the range 8.1-8.3, slightly higher than that of Mrk 71.…”

Section: Introductionmentioning

confidence: 99%

AHSTStudy of the Stellar Populations in the Cometary Dwarf Irregular Galaxy NGC 2366

Thuan

Izotov

2005

ApJ

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We present Vand I photometry of the resolved stars in the cometary dwarf irregular galaxy NGC 2366, using Wide Field Planetary Camera 2 images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram reaches down to I $ 26:0 mag. It reveals not only a young population of blue main-sequence stars (age P30 Myr) but also an intermediate-age population of blue and red supergiants (20 Myr P age P100 Myr) and older evolved populations of asymptotic giant branch (AGB) stars (age k100 Myr) and red giant branch (RGB) stars (age k1 Gyr). The measured magnitude I ¼ 23:65 AE 0:10 mag of the RGB tip results in a distance modulus m À M ¼ 27:67 AE 0:10, which corresponds to a distance of 3:42 AE 0:15 Mpc, in agreement with previous distance determinations. The youngest stars are associated with the bright complex of H ii regions NGC 2363 (=Mrk 71) in the southwest extremity of the galaxy. As a consequence of the diffusion and relaxation processes of stellar ensembles, the older the stellar population is, the smoother and more extended is its spatial distribution. An underlying population of older stars is found throughout the body of NGC 2366. The most notable feature of this older population is the presence of numerous relatively bright AGB stars. The number ratio of AGB to RGB stars and the average absolute brightness of AGB stars in NGC 2366 are appreciably higher than in the BCD VII Zw 403, indicating a younger age of the AGB stars in NGC 2366. In addition to the present burst of age P100 Myr, there has been strong star formation activity in the past of NGC 2366, from $100 Myr to P3 Gyr ago.

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“…NGC 4395 has been studied in detail by Roy et al (1996), who have discovered that there is no global O/H abundance gradient across the disc. They explained this in terms of a large scale redistribution of interstellar matter over a timescale of a few galactic rotations.…”

Section: Introductionmentioning

confidence: 99%

“…Kennicutt & Garnett 1996) because of either the spectroscopic technique or the few lines studied (i.e. Roy et al 1996or Scowen et al 1992) by direct imaging. In this paper we aim to complete these earlier studies by observing a significant number of H  regions in several emission lines in order to be able to extract statistical conclusions about the star formation trends that occur in spiral galaxies.…”

Section: Introductionmentioning

confidence: 99%