A Catalog of OB Associations in the spiral galaxy NGC 300

Pietrzyński, G.; Gieren, W.; Fouqué, P.; Pont, F.

doi:10.1051/0004-6361:20010401

Cited by 47 publications

(76 citation statements)

References 11 publications

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“…Substructure had already been found in early catalogs of associations made by eye (Blaauw 1964), but also by Bresolin et al (1998) and Pietrzyński et al (2001Pietrzyński et al ( , 2005, who both find that associations larger than 200 pc can be separated into smaller denser groups. We only find one association of roughly 200 pc in diameter, #151, and visual inspection indeed reveals that it could be broken into smaller pieces of high density.…”

Section: Sizementioning

confidence: 82%

“…Nevertheless, we suspect the differences are largely related to the instrumental set-up used to build the input photometric catalogs and the distance to the subject galaxy. Pietrzyński et al (2001Pietrzyński et al ( , 2005 already pointed out that the typical sizes derived for the OB associations in the Sculptor Group (NGC 300 and NGC 7793 galaxies) are larger than in the Local Group.…”

Section: Comments On Individual Associationsmentioning

confidence: 99%

“…To use a homogeneous scale, for each galaxy-detector combination we convert the pixel scale into parsecs per pixel. Different symbols indicate different galaxies: IC 1613 (Garcia et al 2009;Borissova et al 2004;Ivanov 1996), NGC 6822 (Wilson 1992;Ivanov 1996), M 33 (Wilson 1991), M 31 (Magnier et al 1993;Ivanov 1996), NGC 300 (Pietrzyński et al 2001), NGC 7793 (Pietrzyński et al 2005), and the sample of spiral galaxies of Bresolin et al (1998). Bresolin et al 1998 is not included because they provided no information about V limit .…”

Section: Comments On Individual Associationsmentioning

confidence: 99%

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The young stellar population of IC 1613

García

Herrero

Castro

et al. 2010

A&A

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Context. To understand the structure and evolution of massive stars, systematic surveys of the Local Group galaxies have been undertaken, to find these objects in environments of different chemical abundances. We focus on the metal-poor irregular galaxy IC 1613 to analyze the stellar and wind structure of its low-metallicity massive stars. We ultimately aim to study the metallicitydependent driving mechanism of the winds of blue massive stars and use metal-poor massive stars of the Local Volume as a proxy for the stars in the early Universe. Aims. In a previous paper we produced a list of OB associations in IC 1613. Their properties are not only a powerful aid towards finding the most interesting candidate massive stars, but also reveal the structure and recent star formation history of the galaxy. We characterize these OB associations and study their connection with the galactic global properties. Methods. The reddening-free Q parameter is a powerful tool in the photometric analysis of young populations of massive stars, since it exhibits a smaller degree of degeneracy with OB spectral types than the B − V color. The color-magnitude diagram (Q vs. V) of the OB associations in IC 1613 is studied to determine their age and mass, and confirm the population of young massive stars. Results. We identified more than 10 stars with M ≥ 50 M . Spectral classification available for some of them confirm their massive nature, yet we find the common discrepancy with the spectroscopically derived masses. There is a general increasing trend of the mass of the most massive member with the number of members of each association, but not with the stellar density. The average diameter of the associations of this catalog is 40 pc, half the historically considered typical size of OB associations. Size increases with the association population. The distribution of the groups strongly correlates with that of neutral and ionized hydrogen. We find the largest dispersion of association ages in the bubble region of the galaxy where hydrogen is abundant, implying that recent star formation has proceeded over a longer period of time than in the rest of the galaxy, and is still ongoing. Very young associations are found at the west of the galaxy far from the bubble region, traditionally considered the sole locus of star formation, but still rich in neutral hydrogen. Conclusions. The contrast in the stellar properties derived from photometry and spectroscopy (when the latter is available) shows that the Q pseudo-color is very useful for estimating the parameters of OB stars when only photometric observations exist. This work helped define an extensive pool of candidate OB stars for subsequent spectroscopic analyses designed to study the structure and winds of metal-poor massive stars.

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Section: Sizementioning

confidence: 82%

Section: Comments On Individual Associationsmentioning

confidence: 99%

Section: Comments On Individual Associationsmentioning

confidence: 99%

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The young stellar population of IC 1613

García

Herrero

Castro

et al. 2010

A&A

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“…of its stellar content -recent surveys include blue supergiants (Bresolin et al 2002a), Cepheids ), OB associations (Pietrzyński et al 2001) and Supernova remnants (Pannuti et al 2001).…”

Section: Introductionmentioning

confidence: 99%

A large Wolf-Rayet population in NGC 300 uncovered by VLT-FORS2

Schild

Crowther

Abbott

et al. 2003

A&A

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Abstract.We have detected 58 Wolf-Rayet candidates in the central region of the nearby spiral galaxy NGC 300, based on deep VLT-FORS2 narrow-band imaging. Our survey is close to complete except for heavily reddened WR stars. Of the objects in our list, 16 stars were already spectroscopically confirmed as WR stars by Schild & Testor and Breysacher et al., to which 4 stars are added using low resolution FORS2 datasets. The WR population of NGC 300 now totals 60, a threefold increase over previous surveys, with WC/WN ≥ 1/3, in reasonable agreement with Local Group galaxies for a moderately sub-solar metallicity. We also discuss the WR surface density in the central region of NGC 300. Finally, analyses are presented for two apparently single WC stars -#29 (alias WR3, WC5) and #48 (alias WR13, WC4) located close to the nucleus, and at a deprojected radius of 2.5 kpc, respectively. These are among the first models of WR stars in galaxies beyond the Local Group, and are compared with early WC stars in our Galaxy and LMC.

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“…Hierarchical structure on large scales was observed for whole OB associations in the LMC (Feitzinger & Braunsfurth 1984), HII regions in 19 galaxies (Feitzinger & Galinski 1987) and 93 galaxies (Sánchez & Alfaro 2008), stellar groupings determined from nearneighbor path linkage in M31 (Battinelli et al 1996), NGC 300 (Pietrzyn'ski et al 2001), and in seven other galaxies (Bresolin et al 1998), and star complexes using flux contours in M51 (Bastian et al 2005) and in nine other galaxies (Gusev 2002). It was also observed using stellar density contours in the LMC (Maragoudaki et al 1998) and M33 (Ivanov 2005), and box counting techniques in 10 galaxies (Elmegreen & Elmegreen 2001), 14 galaxies (Elmegreen et al 2014) and at high resolution in NGC 628 (Elmegreen et al 2006).…”

Section: Introductionmentioning

confidence: 97%

On the Dispersal of Young Stellar Hierarchies

Elmegreen

2018

ApJ

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Hierarchical structure in young star fields has been demonstrated in a variety of ways, including two point correlation functions (TPCFs) that are power laws for spatial scales up to at least several hundred parsecs. As the stars age, this power law decreases in slope until it becomes nearly flat at ∼ 100 Myr, at which point the hierarchical structure has disappeared. The fact that the TPCF remains nearly a power law during this time implies that the dispersal mechanism is somewhat independent of scale. This rules out dispersal by random stellar motions at either the local gas turbulent speed or a constant speed, because in both cases the hierarchy would disappear at small scales first, causing the TPCF to bend over. Destruction by shear has the right property as the shear rate in a galaxy is independent of scale for kpc-size regions, but shear converts the hierarchy into an azimuthal stream which still has a power-law TPCF. What does explain the observation is the overlapping of several independent hierarchies from successive generations of star formation in the same region. If stellar age is determined from magnitude intervals on the main sequence of a color-magnitude diagram, or if clusters ages are grouped together logarithmically into bins, then multiple generations will overlap more and more as the grouped populations age, and this overlap will lower the spatial correlations between group members. Models of these processes illustrate their relative roles in removing the appearance of young stellar hierarchies.

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A Catalog of OB Associations in the spiral galaxy NGC 300

Cited by 47 publications

References 11 publications

The young stellar population of IC 1613

The young stellar population of IC 1613

A large Wolf-Rayet population in NGC 300 uncovered by VLT-FORS2

On the Dispersal of Young Stellar Hierarchies

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