Quantitative Spectroscopy of Blue Supergiants in Metal-Poor Dwarf Galaxy NGC 3109

Hosek, Matthew W.; Kudritzki, Rolf‐Peter; Bresolin, Fabio; Urbaneja, M. A.; Evans, Christopher J.; Pietrzyński, G.; Gieren, W.; Przybilla, N.; Carraro, G.

doi:10.1088/0004-637x/785/2/151

Cited by 58 publications

(75 citation statements)

References 83 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, the independent works of Garcia et al (2014) and Hosek et al (2014) have found evidence that the Fe abundance in IC 1613 and NGC 3109 may be higher than the 1/7Fe value inferred from oxygen. Since Fe is the main driver of the massloss, this mismatch could explain the strong-wind problem.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

OB stars at the lowest Local Group metallicity

Camacho

García

Herrero

2015

A&A

View full text Add to dashboard Cite

Context. Massive stars play an important role in the chemical and dynamical evolution of the Universe. The first metal-poor stars may have started the reionization of the Universe. To understand these early epochs it is necessary to know the behavior and the physical properties of massive stars in very metal-poor environments. We focus on the massive stellar content of the metal-poor irregular galaxy Sextans A. Aims. Our aim is to find and classify OB stars in Sextans A, so as to later determine accurate stellar parameters of these blue massive stars in this low-metallicity region (Z ∼ 0.1 Z ). Methods. Using UBV photometry, the reddening-free index Q and GALEX imaging, we built a list of blue massive star candidates in Sextans A. We obtained low-resolution (R ∼ 1000) GTC-OSIRIS spectra for a fraction of them and carried out spectral classification. For the confirmed O-stars, we derived preliminary stellar parameters. Results. The target selection criteria and observations were successful and have produced the first spectroscopic atlas of OB-type stars in Sextans A. From the whole sample of 18 observed stars, 12 were classified as early OB-types, including 5 O-stars. The radial velocities of all target stars are in agreement with their Sextans A membership, although three of them show significant deviations. We determined the stellar parameters of the O-type stars using the stellar atmosphere code FASTWIND and revisited the sub-SMC temperature scale. Two of the O-stars are consistent with relatively strong winds and enhanced helium abundances, although results are not conclusive. We discuss the position of the OB stars in the HRD. Initial stellar masses run from slightly below 20 up to 40 solar masses. Conclusions. The target selection method worked well for Sextans A. The stellar temperatures are consistent with findings in other galaxies. Some of the targets deserve follow-up spectroscopy because of indications of a runaway nature, an enhanced helium abundance, or a relatively strong wind. We observe a correlation between HI and OB associations similar to the irregular galaxy IC 1613, confirming the previous result that the most recent star formation of Sextans A is currently ongoing near the rim of the H i cavity.

show abstract

Section: Introductionmentioning

confidence: 97%

“…In fact, Sextans A is the Local Group galaxy where the most Fe-poor young stars have been found to date (see Fig. 16, Hosek et al 2014). For this reason, Sextans A offers the unique opportunity to study massive stars in a really metal-poor environment.…”

Section: Introductionmentioning

confidence: 99%

OB stars at the lowest Local Group metallicity

Camacho

García

Herrero

2015

A&A

View full text Add to dashboard Cite

show abstract

“…In recent years, this new method has been successfully applied to galaxies out to a distance of 7 Mpc (Urbaneja et al 2008;U et al 2009;Kudritzki et al 2012Kudritzki et al , 2013Kudritzki et al , 2014Hosek et al 2014).…”

Section: Introductionmentioning

confidence: 99%

The flux-weighted gravity-luminosity relationship of blue supergiant stars as a constraint for stellar evolution

Meynet

Kudritzki

Georgy

2015

A&A

Self Cite

View full text Add to dashboard Cite

Context. The flux-weighted gravity-luminosity relationship (FGLR) of blue supergiant stars (BSG) links their absolute magnitude to the spectroscopically determined flux-weighted gravity log g/T 4 eff . BSG are the brightest stars in the universe at visual light and the application of the FGLR has become a powerful tool for determining extragalactic distances. Aims. Observationally, the FGLR is a tight relationship with only small scatter. It is, therefore, ideal for using as a constraint for stellar evolution models. The goal of this work is to investigate whether stellar evolution can reproduce the observed FGLR and to develop an improved foundation for the FGLR as an extragalactic distance indicator. Methods. We used different grids of stellar models for initial masses between 9 and 40 M and for metallicities between Z = 0.002 and 0.014, with and without rotation, which were computed with various mass loss rates during the red supergiant phase. For each of these models, we discuss the details of post-main sequence evolution and construct theoretical FGLRs by means of population synthesis models that we then compare with the observed FGLR. Results. In general, the stellar evolution model FGLRs agree reasonably well with the observed one. There are, however, differences between the models, in particular with regard to the shape and width (scatter) in the flux-weighted gravity-luminosity plane. The best agreement is obtained with models that include the effects of rotation and assume that the large majority, if not all, of the observed BSG evolve toward the red supergiant phase and that only a few are evolving back from this stage. The effects of metallicity on the shape and scatter of the FGLR are small. Conclusions. The shape, scatter, and metallicity dependence of the observed FGLR are explained well by stellar evolution models. This provides a solid theoretical foundation for using this relationship as a robust extragalactic distance indicator.

show abstract

“…No abundance gradient was found neither in NGC 3109 nor in the supergiants stars analyzed by Evans et al (2007) and Hosek et al (2014 As a result of this work we find that the predicted O, N, and Ne enrichment in PNe should be analyzed more deeply in stellar evolution models. The different models explored here agree in some aspects with the results of observations and disagree in others.…”

Section: )mentioning

confidence: 59%

“…PNe show no gradient either, but this is expected as the central stars modified their original O abundance. A chemical gradient was not found by Evans et al (2007) and Hosek et al (2014) either in their analysis of the chemistry of supergiant stars. Therefore all the material in the bar of the galaxy, which is rotating with a velocity gradient of about 17 km s −1 per kpc, seems well mixed (possibly due to the action of the bar).…”

Section: Is There a Relation Between The Kinematicsmentioning

confidence: 84%

Kinematic and chemical study of planetary nebulae and H II regions in NGC 3109

Flores-Durán

Peña

Ruíz

2017

A&A

View full text Add to dashboard Cite

Aims. We present high-resolution spectroscopy of a number of planetary nebulae (PNe) and H ii regions distributed along the dwarf irregular galaxy NGC 3109 and compare their kinematical behavior with that of H i data. We aim to determine if there is a kinematical connection among these objects. We also aim to determine the chemical composition of some PNe and H ii regions in this galaxy and discuss it in comparison with stellar evolution models.Methods. Data for eight PNe and one H ii region were obtained with the high-resolution spectrograph Magellan Inamori Kyocera Echelle (MIKE) at Las Campanas Observatory, Chile. Data for three PNe, six compact H ii regions, and nine knots or clumps in extended H ii regions were obtained with the high-resolution spectrograph Manchester Echelle Spectrometer (MES) attached to the 2.1m telescope at the Observatorio Astronómico Nacional, SPM, B.C., Mexico. An additional object was obtained from The SPM Catalogue of Extragalactic Planetary Nebulae. Thus, in total we have high-quality data for nine of the 20 PNe detected in this galaxy, and many H ii regions. In the wavelength calibrated spectra, the heliocentric radial velocities were measured with a precision better than 7.8 km s −1 . Data for blue supergiant stars were collected from the literature to be included in the analysis. The heliocentric radial velocities of the different objects were compared to the velocities of the H i disk at the same position. Physical conditions and ionic abundances of PNe and H ii regions were obtained from the emission lines, and we used recent ionization correction factors to derive the total chemical abundances.Results. From the analysis of radial velocities we found that H ii regions in NGC 3109 share the kinematics of the H i disk at the same projected position with very low dispersion in velocities. Blue supergiant stars and PNe rotate in the same direction as the H i disk but these objects have much larger dispersion; this larger dispersion is possibly because these objects belong to a different population that is located in the central stellar bar reported for this galaxy. From the chemical abundance determinations we demonstrate that PNe are enriched in O and Ne. The average O abundance in H ii regions is 12 + log O/H = 7.74 ± 0.09 and PNe show significantly higher oxygen abundance by 0.43 dex in average. Ne abundance are about three times larger in PNe than in H ii regions. This is a very important result showing that because of the low metallicity in the galaxy, O and Ne in PNe have been enriched by their progenitors in nucleosynthesis processes and brought to the surface during third dredge-up events. Our PN abundances are better reproduced by some nonstandard stellar evolution models for a metallicity of Z = 0.001, similar to the metallicity of H ii regions. Abundances in H ii regions show no metallicity gradient in this galaxy. We discuss a possible connection between the kinematics and chemistry.

show abstract

Quantitative Spectroscopy of Blue Supergiants in Metal-Poor Dwarf Galaxy NGC 3109

Cited by 58 publications

References 83 publications

OB stars at the lowest Local Group metallicity

OB stars at the lowest Local Group metallicity

The flux-weighted gravity-luminosity relationship of blue supergiant stars as a constraint for stellar evolution

Kinematic and chemical study of planetary nebulae and H II regions in NGC 3109

Contact Info

Product

Resources

About