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

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

doi:10.1051/0004-6361/201322921

Cited by 6 publications

(5 citation statements)

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“…The MAssive Stars in Galactic Obscured MAssive clusterS (MASGOMAS) is an initiative to look for massive clusters by identifying over-densities of OB-star candidates as young stellar cluster candidates in the 2MASS and other IR catalogues. In the initial stages of the project, using a set of near-infrared photometric cuts (K S < 12.0, (J − K S ) > 1.0 and the reddening-free parameter Q IR between -0.2 and 0.2; see Comerón & Pasquali 2005;Negueruela & Schurch 2007, and Section 2), we discovered one massive cluster in the direction of the close end of the Galactic Bar (Masgomas-1; Ramírez Alegría et al 2012) and one cluster with two cores of massive star formation (Masgomas-4;Ramírez Alegría et al 2014b).…”

Section: Introductionmentioning

confidence: 78%

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Identifying two groups of massive stars aligned in the $l\sim38^{\circ}$ Galactic direction

Alegría,

Herrero,

Rübke

et al. 2018

Preprint

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Context. Recent near-infrared data have contributed to unveil massive and obscured stellar populations in both new and previously known clusters in our Galaxy. These discoveries 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 Hand K-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-Rayet (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, and Masgomas-6b, 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 can not clearly identify whether these massive stars form clusters or associations.

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Section: Introductionmentioning

confidence: 78%

“…We classify our spectra following the same procedure than for Masgomas-1 and Masgomas-4 (Ramírez Alegría et al 2012, 2014b. Using spectral libraries with similar resolution than LIRIS spectra, we identify spectral lines and compare the shapes and depths.…”

Section: Spectral Classificationmentioning

confidence: 99%

Identifying two groups of massive stars aligned in the $l\sim38^{\circ}$ Galactic direction

Alegría,

Herrero,

Rübke

et al. 2018

Preprint

View full text Add to dashboard Cite

show abstract

“…The MAssive Stars in Galactic Obscured MAssive clusterS (MASGOMAS) is an initiative to look for massive clusters by identifying over-densities of OB-star candidates as young stellar cluster candidates in the 2MASS and other IR catalogues. In the initial stages of the project, using a set of near-infrared photometric cuts (magnitude K S < 12.0, colour (J − K S ) > 1.0 and the reddening-free parameter Q IR between -0.2 and 0.2, see Comerón & Pasquali 2005;Negueruela & Schurch 2007, and Sect. 2), we discovered one massive cluster in the direction of the close end of the Galactic Bar (Masgomas-1; Ramírez Alegría et al 2012) and one cluster with two cores of massive star formation (Masgomas-4;Ramírez Alegría et al 2014b).…”

Section: Introductionmentioning

confidence: 89%

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

Alegría

Herrero

Rübke

et al. 2018

A&A

Self Cite

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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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“…This way we get snapshots of stellar evolution at different times and, post-main sequence evolution being much faster than hydrogen-burning, the progenitors and evolution of evolved massive stars can be better identified. This approach can be conducted by studying young massive clusters (Martins et al 2007(Martins et al , 2008; Davies et al 2007Davies et al , 2008Negueruela et al 2010;Liermann et al 2012;Davies et al 2012b,a;Borissova et al 2012;Ramírez Alegría et al 2012, 2014b.…”

Section: Introductionmentioning

confidence: 99%

“…The ESO VISTA Variables in the Vía Láctea (VVV) survey is a near-infrared photometric survey of the Galaxy (Minniti et al 2010;Saito et al 2012;Hempel et al 2014). Several young massive clusters have been discovered (Borissova et al 2011;Chené et al 2012) and follow-up spectroscopy has allowed the identification of massive stars in a number of them (Chené et al 2013(Chené et al , 2015Ramírez Alegría et al 2014b, 2016. Hervé et al (2016) presented preliminary results on the analysis of WR stars in four clusters.…”

Section: Introductionmentioning

confidence: 99%

Massive stars in the young cluster VVV CL074

Martins

Chené

Bouret

et al. 2019

A&A

Self Cite

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Context. The evolution of massive stars is not fully constrained. Studies of young massive clusters hosting various populations of massive stars can help refine our understanding of the life and fate of massive stars. Aims. In this context, our goal is to study the massive stellar content of the young massive cluster VVV CL074. Methods. We obtained K-band spectroscopy of the brightest cluster members in order to identify the massive star population. We also determined the stellar properties of the cluster's massive stars to better quantify the evolutionary sequences linking different types of massive stars. We collected integral field spectroscopy of selected fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the massive stars from analysis with atmosphere models computed with the code CMFGEN. Results. We uncover a population of 25 early-type (OB and Wolf-Rayet) stars, 19 being newly discovered by our observations out of which 15 are likely cluster members. The cluster's spectrophotometric distance is 10.2±1.6 kpc, placing it close to the intersection of the galactic bar and the Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young massive clusters identified so far. Among the massive stars population, three objects are Wolf-Rayet stars, the remaining are O and B stars. From the Hertzsprung-Russell diagram we find that most stars have an age between 3 and 6 Myr according to the Geneva evolutionary tracks. WN8 and WC8-9 stars are the descendants of stars with initial masses between 40 and 60 M ⊙ . The massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older. From the comparison of the massive stars populations in these four clusters, one concludes that galactic stars with an initial mass in the range 40 to 60 M ⊙ likely go through a WN8-9 phase. ⋆ Based on observations conducted at ESO on the Very Large Telescope under program 099.D-0161(B).

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

Cited by 6 publications

References 60 publications

Identifying two groups of massive stars aligned in the $l\sim38^{\circ}$ Galactic direction

Identifying two groups of massive stars aligned in the $l\sim38^{\circ}$ Galactic direction

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

Massive stars in the young cluster VVV CL074

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