Characterizing the Stellar Population in NGC 1705‐1

Vázquez, Gerardo A.; Leitherer, Claus; Heckman, Timothy M.; Lennon, D. J.; Mello, D. F. de; Meurer, G. R.; Martin, Crystal L.

doi:10.1086/379805

Cited by 36 publications

(56 citation statements)

References 53 publications

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“…There are Send offprint requests to: C. Trundle, e-mail: ct@ing.iac.es important reasons for this extension, among them the fact that the B-type stars are important contributors to the UV spectrum of continuous starforming and intermediate age stellar populations (deMello et al 2000). In fact the UV spectra of the stars discussed in the present paper have been used to constrain the age of the metal poor super star cluster NGC 1705-1 (Vazquez et al 2003). However what is more relevant to the present paper is that B-type supergiants in the SMC provide important information on mass-loss and stellar evolution in a low metallicity environment.…”

Section: Introductionmentioning

confidence: 86%

Understanding B-type supergiants in the low metallicity environment of the SMC

Trundle

Lennon

Puls

et al. 2004

A&A

108

182

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Abstract. Spectroscopic analyses of 7 SMC B-type supergiants and 1 giant have been undertaken using high resolution optical data obtained on the  with . , a non-LTE, spherical, line-blanketed model atmosphere code was used to derive atmospheric and wind parameters of these stars as well as their absolute abundances. Mass-loss rates, derived from H α profiles, are in poor agreement with metallicity dependent theoretical predictions. Indeed the wind-momenta of the SMC stars appear to be in good agreement with the wind-momentum luminosity relationship (WLR) of Galactic B-type stars, a puzzling result given that line-driven wind theory predicts a metallicity dependence. However the galactic stars were analysed using unblanketed model atmospheres which may mask any dependence on metallicity. A mean nitrogen enhancement of a factor of 14 is observed in the supergiants whilst only an enrichment of a factor of 4 is present in the giant, AV216. Similar excesses in nitrogen are observed in O-type dwarfs and supergiants in the same mass range, suggesting that the additional nitrogen is produced while the stars are still on the main-sequence. These nitrogen enrichments can be reproduced by current stellar evolution models, which include rotationally induced mixing, only if large initial rotational velocities of 300 km s −1 are invoked. Such large rotational velocities appear to be inconsistent with observed v sin i distributions for O-type stars and B-type supergiants. Hence it is suggested that the currently available stellar evolution models require more efficient mixing for lower rotational velocities.

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Section: Introductionmentioning

confidence: 86%

Understanding B-type supergiants in the low metallicity environment of the SMC

Trundle

Lennon

Puls

et al. 2004

A&A

108

182

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“…It also explains the higher outflow speeds for C IIλ1335 relative to Al IIλ1671 and Si IIλ1260 (Schwartz et al 2006) as C IIλ1335 is the strongest feature. Lastly, in the work by Vázquez et al (2004), the lines with the highest measured equivalent widths are preferentially those with the highest ionization energies. This result thus appears to be consistent throughout a wide range of galaxy types and absorption features.…”

Section: Outflow Velocity Distributionsmentioning

confidence: 97%

Observations of Starburst Galaxies With Far-Ultraviolet Spectrographic Explorer: Galactic Feedback in the Local Universe

Grimes

Heckman

Aloisi

et al. 2009

ApJS

160

200

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We have analyzed FUSE (905-1187Å) spectra of a sample of 16 local starburst galaxies. These galaxies cover almost three orders of magnitude in starformation rates and over two orders of magnitude in stellar mass. Absorption features from the stars and interstellar medium are observed in all the spectra. The strongest interstellar absorption features are generally blue-shifted by ∼ 50 to 300 km s −1 , implying the almost ubiquitous presence of starburst-driven galactic winds in this sample. The outflow velocites increase with both the star formation rate and the star formation rate per unit stellar mass, consistent with a galactic wind driven by the population of massive stars. We find outflowing coronal-phase gas (T ∼ 10 5.5 K) detected via the O VI absorption-line in nearly every galaxy. The O VI absorption-line profile is optically-thin, is generally weak near the galaxy systemic velocity, and has a higher mean outflow velocity than seen in the lower ionization lines. The relationship between the line width and column density for the O VI absorbing gas is in good agreement with expectations for radiatively cooling and outflowing gas. Such gas will be created in the interaction of the hot out-rushing wind seen in X-ray emission and cool dense ambient material. O VI emission is not generally detected in our sample, suggesting that radiative cooling by the coronal gas is not dynamically significant in draining energy from galactic winds. We find that the measured outflow velocities in the HI and HII phases of the interstellar gas in a given galaxy increase with the strength (equivalent width) of the absorption feature and not with the -2 -ionization potential of the species. The strong lines often have profiles consisting of a broad and optically-thick component centered near the galaxy systemic velocity and weaker but highly blue-shifted absorption. This suggests that the outflowing gas with high velocity has a lower column density than the more quiescent gas, and can only be readily detected in the strongest absorption lines. From direct observations below the Lyman edge in the galaxy rest-frame, we find no evidence of Lyman continuum radiation escaping from any of the galaxies in the sample. Moreover, the small escape fraction of light in the center of the strong C II absorption feature confirms the high opacity below the Lyman limit in the neutral ISM. The absolute fraction of escaping Lyman continuum photons is typically <1%. This sample provides a unique window on the global properties of local star-forming galaxies as observed in the far-UV and also provides a useful comparison sample for understanding spectra of high redshift star-forming galaxies.

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“…The clusters in NGC 1569 and NGC 1705 are significantly younger than those in the spirals, and age estimates from integrated light are more uncertain for these clusters due to the rapid, metallicity-dependent changes in integrated colours at very young ages. For NGC 1705-1 we initially adopt an age of 12 Myr, based on STIS spectroscopy (Vazquez et al 2004). For NGC 1569-A we assume an age of 5 Myr (Origlia et al 2001;Westmoquette et al 2007) and for NGC 1569-B we assume 15 Myr (Anders et al 2004;Larsen et al 2008).…”

Section: Selection Of the Samplementioning

confidence: 99%

Resolved photometry of extragalactic young massive star clusters

Larsen

Mink

Eldridge

et al. 2011

A&A

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Aims. We present colour-magnitude diagrams (CMDs) of young massive star clusters in several galaxies located well beyond the Local Group. The richness of these clusters allows us to obtain large samples of post-main sequence stars and test how well the observed CMDs are reproduced by canonical stellar isochrones. Methods. We use imaging of seven clusters in the galaxies NGC 1313, NGC 1569, NGC 1705, NGC 5236 and NGC 7793 obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope and carry out PSF-fitting photometry of individual stars in the clusters. The clusters have ages in the range ∼(5−50) × 10 6 years and masses of ∼10 5 M -10 6 M . Although crowding prevents us from obtaining photometry in the inner regions of the clusters, we are still able to measure up to 30-100 supergiant stars in each of the richest clusters. The resulting CMDs and luminosity functions are compared with photometry of artificially generated clusters, designed to reproduce the photometric errors and completeness as realistically as possible.Results. In agreement with previous studies, our CMDs show no clear gap between the H-burning main sequence and the Heburning supergiant stars, contrary to predictions by common stellar isochrones. In general, the isochrones also fail to match the observed number ratios of red-to-blue supergiant stars, although the difficulty of separating blue supergiants from the main sequence complicates this comparison. In several cases we observe a large spread (1-2 mag) in the luminosities of the supergiant stars that cannot be accounted for by observational errors. We find that this spread can be reproduced by including an age spread of ∼(10−30) × 10 6 years in the models. However, age spreads cannot fully account for the observed morphology of the CMDs and other processes, such as the evolution of interacting binary stars, may also play a role. Conclusions. Colour-magnitude diagrams can be successfully obtained for massive star clusters out to distances of at least 4-5 Mpc. Comparing such CMDs with models based on canonical isochrones we find several areas of disagreement. One interesting possibility is that an age spread of up to ∼30 Myr may be present in some clusters. The data presented here may provide useful constraints on models for single and/or binary stellar evolution.

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Characterizing the Stellar Population in NGC 1705‐1

Cited by 36 publications

References 53 publications

Understanding B-type supergiants in the low metallicity environment of the SMC

Understanding B-type supergiants in the low metallicity environment of the SMC

Observations of Starburst Galaxies With Far-Ultraviolet Spectrographic Explorer: Galactic Feedback in the Local Universe

Resolved photometry of extragalactic young massive star clusters

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