Discovery of a young and massive stellar cluster

Alegría, S. Ramírez; Marín-Franch, A.; Herrero, A.

doi:10.1051/0004-6361/201118273

Cited by 14 publications

(15 citation statements)

References 39 publications

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“…The MASGOMAS project focuses on the search of overdensities formed by OB-type star candidates and the characterization of these candidates using near-infrared photometry and spectroscopy. We select the OB-type candidates using three photometric criteria: K S magnitudes less than 12 mag (a limit adopted by the instrument used in our spectroscopic follow-up), red (J − K S ) > 1.0 colours, and a reddening-free parameter Q IR between -0.2 and 0.2 (Ramírez Alegría et al 2012). The adopted Q IR parameter is…”

Section: Candidate Discoverymentioning

confidence: 99%

Identifying two groups of massive stars aligned in thel~ 38° Galactic direction

Alegría

Herrero

Rübke

et al. 2018

A&A

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Context. Recent near-infrared data have contributed to unveiling massive and obscured stellar populations in both new and previously known clusters in our Galaxy. These discoveries have lead us to view the Milky Way as an active star-forming machine. Aims. We look for young massive cluster candidates as over-densities of OB-type stars. The first search, focused on the Galactic direction l = 38°, resulted in the detection of two objects with a remarkable population of OB-type star candidates. Methods. With a modified version of the friends-of-friends algorithm AUTOPOP and using 2MASS and UKIDSS-GPS near-infrared (J, H, and K) photometry for one of our cluster candidates (named Masgomas-6) we selected 30 stars for multi-object and long-slit H and K band spectroscopy. With the spectral classification and the near-infrared photometric data, we derive individual distance, extinction, and radial velocity. Results. Of the 30 spectroscopically observed stars, 20 are classified as massive stars, including OB-types (dwarfs, giants and supergiants), two red supergiants, two Wolf−Rayets (WR122-11 and the new WR122-16), and one transitional object (the LBV candidate IRAS 18576+0341). The individual distances and radial velocities do not agree with a single cluster, indicating that we are observing two populations of massive stars in the same line of sight: Masgomas-6a and Masgomas-6b. The first group of massive stars, located at 3.9$^{+0.4}_{-0.3}$ kpc, contains both Wolf−Rayets and most of the OB-dwarfs; the second group, located at 9.6 ± 0.4 kpc, hosts the LBV candidate and an evolved population of supergiants. We are able to identify massive stars at two Galactic arms, but we cannot clearly identify whether these massive stars form clusters or associations.

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Section: Candidate Discoverymentioning

confidence: 99%

Identifying two groups of massive stars aligned in thel~ 38° Galactic direction

Alegría

Herrero

Rübke

et al. 2018

A&A

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“…The catalogues used for spectral classification were Hanson et al (1996, K band) and Hanson et al (1998, H band), for OB-type stars, and Meyer et al (1998); Wallace & Hinkle (1997) for late-type stars. For the assigned spectral type we assume an error of ±2 subtypes, similar to Hanson et al (2010), Negueruela et al (2010), andRamírez Alegría et al (2012). Table 2 provides the coordinates, infrared magnitudes, and spectral types of the spectroscopically observed stars.…”

Section: Spectral Classificationmentioning

confidence: 99%

“…The mass function was derived from the luminosity function and the contribution from the galactic disc stellar population was corrected using the observed control field (from LIRIS images). The cluster and control field photometries were cut in J < 16.5 mag, H < 15.5 mag, and K < 14.5 mag, to assure a completeness close to 1.0, following the same procedure described by Ramírez Alegría et al (2012).…”

Section: Mass and Age Estimatesmentioning

confidence: 99%

Masgomas-4: Physical characterization of a double-core obscured cluster with a massive and very young stellar population

Alegría

Marín-Franch

Herrero

2014

A&A

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Context. The discovery of new, obscured massive star clusters has changed our understanding of the Milky Way star-forming activity from a passive to a very active star-forming machine. The search for these obscured clusters is strongly supported by the use of all-sky, near-IR surveys. Aims. The main goal of the MASGOMAS project is to search for and study unknown, young, and massive star clusters in the Milky Way, using near-IR data. Here we try to determine the main physical parameters (distance, size, total mass, and age) of Masgomas-4, a new double-core obscured cluster. Methods. Using near-IR photometry (J, H, and K S ) we selected a total of 21 stars as OB-type star candidates. Multi-object, near-IR follow-up spectroscopy allowed us to carry out the spectral classification of the OB-type candidates. Results. Of the 21 spectroscopically observed stars, ten are classified as OB-type stars, eight as F-to early G-type dwarf stars, and three as late-type giant stars. Spectroscopically estimated distances indicate that the OB-type stars belong to the same cluster, located at a distance of 1.90 +1.28 −0.90 kpc. Our spectrophotometric data confirm a very young and massive stellar population, with a clear concentration of pre-main-sequence massive candidates (Herbig Ae/Be) around one of the cluster cores. The presence of a surrounding H II cloud and the Herbig Ae/Be candidates indicate an upper age limit of 5 Myr.

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“…this effort was begin with a search of massive young obscured clusters in a limited region of the Milky Way using photometric cuts optimized for the search of OB-stars (Ramírez-Alegría, Marín-Franch & Herrero, 2012). Moreover, the search was limited to stars with Ks < 12.5 to allow a spectroscopic follow-up with LIRIS@GTC.…”

Section: Massive Clusters In the Milky Waymentioning

confidence: 99%

SpS5 - I. Obscured and distant clusters

Hanson¹,

Froebrich

Martins

et al. 2012

Proc. IAU

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Abstract. This first part of Special Session 5 explored the current status of infrared-based observations of obscured and distant stellar clusters in the Milky Way galaxy. Recent infrared surveys, either serendipitously or using targeted searches, have uncovered a rich population of young and massive clusters. However, cluster characterization is more challenging as it must be obtained often entirely in the infrared due to high line-of-sight extinction. Despite this, much is to be gained through the identification and careful analysis of these clusters, as they allow for the early evolution of massive stars to be better constrained. Further, they act as beacons delineating the Milky Way's structure and as nearby, resolved analogues to the distant unresolved massive clusters studied in distant galaxies.

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Discovery of a young and massive stellar cluster

Cited by 14 publications

References 39 publications

Identifying two groups of massive stars aligned in thel~ 38° Galactic direction

Identifying two groups of massive stars aligned in thel~ 38° Galactic direction

Masgomas-4: Physical characterization of a double-core obscured cluster with a massive and very young stellar population

SpS5 - I. Obscured and distant clusters

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