Spectroscopic study of blue compact galaxies

Kong, Xu; Cheng, F. Z.; Weiß, A.; Charlot, S.

doi:10.1051/0004-6361:20021452

Cited by 44 publications

(43 citation statements)

References 32 publications

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“…Haro 15 is a blue compact galaxy that has been well studied at all frequencies, including optical spectroscopy (Hunter & Gallagher 1985;Mazzarrella et al 1991;Kong et al 2002;Shi et al 2005). Schaerer et al (1999) listed Haro 15 as a WR galaxy because of the detection of the He ii λ4686 emission line by Kovo & Contini (1999).…”

Section: Haro 15mentioning

confidence: 99%

Massive star formation in Wolf-Rayet galaxies

López-Sánchez

Esteban

2009

A&A

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Aims. We have performed a comprehensive multiwavelength analysis of a sample of 20 starburst galaxies that show the presence of a substantial population of very young massive stars, most of them classified as Wolf-Rayet (WR) galaxies. In this paper, the second of the series, we present the results of the analysis of long-slit intermediate-resolution spectroscopy of star-formation bursts for 16 galaxies of our sample. Methods. We study the spatial localization of the WR stars in each galaxy. We analyze the excitation mechanism and derive the reddening coefficient, physical conditions, and chemical abundances of the ionized gas. We study the kinematics of the ionized gas to check the rotation/turbulence pattern of each system. When possible, tentative estimates of the Keplerian mass of the galaxies are calculated. Results. Aperture effects and the exact positioning of the slit onto the WR-rich bursts seem to play a fundamental role in their detection. We check that the ages of the last star-forming burst estimated using optical spectra agree with those derived from Hα imagery. Our analysis shows that a substantial fraction of the galaxies exhibit evidence of perturbed kinematics. With respect to the results found in individual galaxies, we remark the detection of objects with different metallicity and decoupled kinematics in Haro 15 and Mkn 1199, the detection of tidal streams in IRAS 08208+2816, Tol 9, and perhaps in SBS 1319+579, and the development of a merging process in both SBS 0926+606 A and Tol 1457-262. Conclusions. All of these results -in combination with those obtained in Paper I -reinforce the hypothesis that interactions with or between dwarf objects is a very important mechanism in triggering massive-star formation in starburst galaxies, especially in dwarf ones. It must be highlighted that only deep and very detailed observations -as presented in this paper -can provide clear evidences that these subtle interaction processes are taking place.

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Section: Haro 15mentioning

confidence: 99%

Massive star formation in Wolf-Rayet galaxies

López-Sánchez

Esteban

2009

A&A

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“…The absorption equivalent widths and continuum fluxes were measured by Kong et al (2002b) according to the procedure outlined in Bica (1988) and Cid Fernandes et al (2001;see Kong et al 2002b for detail). In some spectra, the continuum flux at 5870 Å may be buried underneath the He  λ5876 Å emission line.…”

Section: Input Datamentioning

confidence: 99%

“…In such cases, adjacent wavelength regions were used to estimate the continuum level. The resulting absorption equivalent widths are listed in Table 6 of Kong et al (2002b), and the continuum fluxes in Table 4 of Kong et al (2002b). The errors in the absorption equivalent widths and continuum fluxes must also be included as input parameters.…”

Section: Input Datamentioning

confidence: 99%

Spectroscopic study of blue compact galaxies

Kong

Charlot

Weiß

et al. 2003

A&A

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Abstract. This is the third paper of a series dedicated to the study of the star formation rates, star formation histories, metallicities and dust contents of a sample of blue compact galaxies (BCGs). We constrain the stellar contents of 73 blue compact galaxies by analyzing their continuum spectra and the equivalent widths of strong stellar absorption features using a technique of empirical population synthesis based on a library of observed star-cluster spectra. Our results indicate that blue compact galaxies are typically age-composite stellar systems; in addition to young stars, intermediate-age and old stars contribute significantly to the 5870 Å continuum emission of most galaxies in our sample. The stellar populations of blue compact galaxies also span a variety of metallicities. The ongoing episodes of star formation started typically less than a billion years ago. Some galaxies may be undergoing their first global episode of star formation, while for most galaxies in our sample, older stars are found to contribute up to half the optical emission. Our results suggest that BCGs are primarily old galaxies with discontinuous star formation histories. These results are consistent with the results from deep imaging observations of the color-magnitude diagrams of a few nearby BCGs using HST and large ground-based telescopes. The good quality of our population synthesis fits of BCG spectra allow us to estimate the contamination of the Hα, Hβ, Hγ and Hδ Balmer emission lines by stellar absorption. The absorption equivalent widths measured in the synthetic spectra range from typically 1.5 Å for Hα, to 2-5 Å for Hβ, Hγ, and Hδ. The implied accurate measurements of emission-line intensities will be used in a later study to constrain the star formation rates and gas-phase chemical element abundances of blue compact galaxies.

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“…Therefore, dust reflection of the M82 starburst regions, suggested by strong UV emission (Hoopes et al 2005), is not the dominant emission mechanism in the optical wavelength. Figure 4 compares the observed [N ii]/Hα and [S ii]/Hα ratios of the M82 cap with those of H ii regions (Jansen et al 2000), blue compact galaxies (Kong et al 2002), LINERs (Ho et al 1997), and very extended ionized gas (EIG) in the Coma cluster (Yoshida et al 2012). We find that the line ratios of the M82 cap are similar to those of some EIG knots which have larger [S ii]/Hα ratios than the main sequence of star-forming galaxies.…”

Section: Resultsmentioning

confidence: 99%

“…This fact suggests that the emission line ratios of the (Yoshida et al 2012). The shaded region represents the line ratios of H ii regions of nearby field galaxies (Jansen et al 2000), blue compact galaxies (Kong et al 2002), and LINERs (Ho et al 1997). …”

Section: Resultsmentioning

confidence: 99%

Ionization Source of a Minor-Axis Cloud in the Outer Halo of M82

Matsubayashi

Sugai

Shimono

et al. 2012

ApJ

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The M82 "cap" is a gas cloud at a projected radius of 11.6 kpc along the minor axis of this well-known superwind source. The cap has been detected in optical line emission and X-ray emission and therefore provides an important probe of the wind energetics. In order to investigate the ionization source of the cap, we observed it with the Kyoto3DII Fabry-Perot instrument mounted on the Subaru Telescope. Deep continuum, Hα, [N ii]λ6583/Hα, and [S ii]λλ6716,6731/Hα maps were obtained with subarcsecond resolution. The superior spatial resolution compared to earlier studies reveals a number of bright Hα emitting clouds within the cap. The emission line widths ( 100 km s −1 FWHM) and line ratios in the newly identified knots are most reasonably explained by slow to moderate shocks velocities (v shock = 40-80 km s −1 ) driven by a fast wind into dense clouds. The momentum input from the M82 nuclear starburst region is enough to produce the observed shock. Consequently, earlier claims of photoionization by the central starburst are ruled out because they cannot explain the observed fluxes of the densest knots unless the UV escape fraction is very high (f esc > 60%), i.e., an order of magnitude higher than observed in dwarf galaxies to date. Using these results, we discuss the evolutionary history of the M82 superwind. Future UV/X-ray surveys are expected to confirm that the temperature of the gas is consistent with our moderate shock model.

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Spectroscopic study of blue compact galaxies

Cited by 44 publications

References 32 publications

Massive star formation in Wolf-Rayet galaxies

Massive star formation in Wolf-Rayet galaxies

Spectroscopic study of blue compact galaxies

Ionization Source of a Minor-Axis Cloud in the Outer Halo of M82

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