New Wolf‐Rayet Galaxies with Detection of WC Stars

Huang, Jianfeng; Gu, Qiusheng; Long, Jing; Li, W. D.; Wei, J. Y.; Zheng, Wei

doi:10.1086/306859

Cited by 20 publications

(24 citation statements)

References 35 publications

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“…This seems to indicate an inhomogeneous distribution of the dust within the galaxy, the southern regions being dustier than the remainder of the system. Huang et al (1999) also derived low extinction values in the center of IRAS 08208+2816, which they explained by considering the presence of a galactic wind in the galaxy, but we do not detect these structures in our deep Hα images (see Fig. 10 of Paper I).…”

Section: Physical Conditions Of the Ionized Gasmentioning

confidence: 51%

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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: Physical Conditions Of the Ionized Gasmentioning

confidence: 51%

“…The first spectroscopic data of IRAS 08208+2816 were obtained by Huang et al (1999), who reported the detection of both a nebular and broad He ii λ4686 emission line. They also detected the red WR bump, C iv λ5808, suggesting the presence of both WNL and WCE populations in the starburst.…”

Section: Iras 08208+2816mentioning

confidence: 99%

Massive star formation in Wolf-Rayet galaxies

López-Sánchez

Esteban

2009

A&A

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“…However, Steel et al (1996) note that the galaxy has relatively regular outer isophotes in optical light and that all of the star-forming regions have the same redshift. Steel et al also find approximately the same metallicity for both regions A and B of 12 þ log (O=H) ¼ 8:4 (roughly 1 3 the solar value); using a different slit location, Huang et al (1999) find a metallicity of 12 þ log (O=H) ¼ 8:3. This evidence leads Steel et al to conclude that the star formation in Haro 3 is most likely selfinduced.…”

Section: Introductionmentioning

confidence: 85%

Revealing the Young Starburst in Haro 3 with Radio and Infrared Imaging

et al. 2004

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The Wolf-Rayet galaxy Haro 3 (Mrk 35, NGC 3353) was observed at the near-IR and radio wavelengths as part of an ongoing program to study the earliest stages of starbursts. These observations confirm that the current episode of star formation is dominated by a single region (region A). While there are knots of recent ($10 Myr) star formation outside of region A, the sources of ionizing radiation as observed in both radio and Br observations are almost exclusively associated with region A. The derived ionizing flux implies a star formation rate of %0.6 M yr À1 localized within a radius of $0.1 kpc. A comparison with HST observations indicates that one or more of the star clusters in region A are optically obscured. The star clusters in region A have ages at least as young as $5 Myr, and possibly as young as $0.1 Myr. The star cluster that appears to be the youngest also exhibits a near-IR excess in its colors, possibly indicating natal dust in very close proximity to the ionizing stars. The difference between optical-and radio-determined ionizing fluxes, as well as the near-IR colors, indicates an average extinction value of A V % 2:5 in region A. The total stellar mass associated with the current starburst in region A is inferred from both the near-IR and radio observations to be $10 6 M . The other main stellar concentrations observed in the near-IR (regions B1 and B2) are somewhat older than region A, with ages $8-10 Myr, and the near-IR observations indicate they have stellar masses of $8 ; 10 4 and $2 ; 10 4 M , respectively.

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“…We suspect that maybe knot #1, which hosts the youngest and most powerful burst in the system, is the only area where a substantial population may be present. Thus, aperture effects and the position of the slit can play an important role in the detection of WR features, as some authors have previously pointed out (Huang et al 1999;López-Sánchez et al 2004a,b).…”

Section: Wr Populationmentioning

confidence: 93%

Star formation and stellar populations in the Wolf-Rayet(?) luminous compact blue galaxy IRAS 08339+6517

López-Sánchez¹,

Esteban²,

García‐Rojas³

2006

A&A

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Aims. IRAS 08339+6517 is a luminous infrared and Lyα-emitting starburst galaxy that possesses a dwarf companion object at a projected distance of 56 kpc. An H i tidal tail has recently been detected between both galaxies, suggesting that about 70% of the neutral gas has been ejected from them. Methods. We present deep broad-band optical images, together with narrow band Hα CCD images, and optical intermediate-resolution spectroscopy of both galaxies. Results. The images reveal interaction features between both systems and strong Hα emission in the inner part of IRAS 08339+6517. The chemical composition of the ionized gas of the galaxies is rather similar. The analysis of their kinematics also indicates interaction features and reveals an object that could be a candidate tidal dwarf galaxy or a remnant of an earlier merger. Our data suggest that the H i tail has been mainly formed from material stripped from the main galaxy. We find weak spectral features that could be attributed to the presence of Wolf-Rayet stars in this starburst galaxy and estimate an age of the most recent burst of around 4-6 Myr. A more evolved underlying stellar population, with a minimal age between 100-200 Myr, is also detected and fits an exponential intensity profile. A model which combines 85% young and 15% old populations can explain both the spectral energy distribution and the H i Balmer and He i absorption lines presented in our spectrum. The star formation rate of the galaxy is consistently derived using several calibrations, giving a value of ∼9.5 M yr −1 . Conclusions. IRAS 08339+6517 does satisfy the criteria of a luminous compact blue galaxy, rare objects in the local universe but common at high redshifts, being a very interesting target for detailed studies of galaxy evolution and formation.Key words. galaxies: starburst -galaxies: interactions -galaxies: abundances -galaxies: kinematics and dynamics -stars: Wolf-Rayet IntroductionDetermining the star formation history in galaxies is fundamental for the understanding of their evolution. In nearby galaxies, such as those belonging to the Local Group, it is performed studying the stellar content via color-magnitude diagrams (CMD) and stars as age tracers (see Grebel 1999, and references there in). However, in distant galaxies it is only interpreted by means of spectral synthesis techniques. The analysis of the interstellar medium (ISM) in and around galaxies complements the study of their star formation histories. Star formation activity is stronger in starburst galaxies, where the dominant and very young stellar population could even hide the more evolved stellar population presented in it. The more extreme cases are the blue compact dwarf (BCDs) galaxies, that Table 4 is only available in electronic form at http://www.edpsciences.org have very low metal abundances and exhibit a global starburst activity. Although the majority of these systems possesses an old underlying population with ages of several Gyr (Loose & Thuan 1986), a few of them do not present it, sugges...

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New Wolf‐Rayet Galaxies with Detection of WC Stars

Cited by 20 publications

References 35 publications

Massive star formation in Wolf-Rayet galaxies

Massive star formation in Wolf-Rayet galaxies

Revealing the Young Starburst in Haro 3 with Radio and Infrared Imaging

Star formation and stellar populations in the Wolf-Rayet(?) luminous compact blue galaxy IRAS 08339+6517

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