IJAA  Vol.3 No.2 , June 2013
New Candidate Massive Clusters from 2MASS
Abstract: Massive stars are important for the evolution of the interstellar medium. The detailed study of their properties (such as mass loss, rotation, magnetic fields) is enormously facilitated by samples of these objects in young massive galactic star clusters. Using 2MASS we have searched for so far unknown candidates of red supergiant clusters along the Galactic Plane. Utilising deep high resolution UKIDSS GPS and VISTA VVV data to study colour-magnitude diagrams, we uncover six new massive cluster candidates in the inner Galaxy. If spectroscopically confirmed as real clusters, two of them could be part of the Scutum-Complex. One cluster candidate has a number of potential red supergiant members comparable to RSGC1 and 3. Our investigation of UKIDSS data reveals for the first time the main sequence of the massive cluster RSGC2. The stars of the sequence show an increased projected density at the same position as the known red supergiants in the cluster and have E(J-K) = 1.6 mag. This either indicates an unusual extinction law along the line of sight or a much lower near infrared extinction to the cluster than previously estimated in the literature. We suggest that psf-photometry in UKIDSS images might be able to uncover the main sequence of other RSGC clusters.
Cite this paper: D. Froebrich, "New Candidate Massive Clusters from 2MASS," International Journal of Astronomy and Astrophysics, Vol. 3 No. 2, 2013, pp. 161-173. doi: 10.4236/ijaa.2013.32018.

[1]   I. Brott, S. E. de Mink, M. Cantiello, N. Langer, A. Koter, C. J. Evans, I. Hunter, C. Trundle, et al., “Rotating Massive Main-Sequence Stars. I. Grids of Evolutionary Models and Isochrones,” Astronomy & Astrophysics (A&A), Vol. 530, 2011, p. 115. doi:10.1051/0004-6361/201016113

[2]   J. S. Clark, I. Negueruela, P. A. Crowther and S. P. Goodwin, “On the Massive Stellar Population of the Super Star Cluster Westerlund 1,” Astronomy & Astrophysics (A&A), Vol. 434, No. 3, 2005, pp. 949-969. doi:10.1051/0004-6361:20042413

[3]   D. F. Figer, J. W. MacKenty, M. Robberto, K. Smith, F. Najarro, R. P. Kudritzki and A. Herrero, “Discovery of an Extraordinarily Massive Cluster of Red Supergiants,” The Astrophysical Journal, Vol. 643, No. 2, 2006, pp. 1166-1179. doi:10.1086/503275

[4]   B. Davies, D. F. Figer, R. P. Kudritzki and J. MacKenty, “A Massive Cluster of Red Supergiants at the Base of the Scutum-Crux Arm,” The Astrophysical Journal, Vol. 671, No. 1, 2007, pp. 781-801. doi:10.1086/522224

[5]   J. S. Clark, I. Negueruela, B. Davies and V. M. Larionov, “A Third Red Supergiant Rich Cluster in the ScutumCrux Arm,” Astronomy & Astrophysics (A&A), Vol. 498, No. 1, 2009, pp. 109-114. doi:10.1051/0004-6361/200911945

[6]   I. Negueruela, C. Gonzalez-Fernandez, A. Marco, J. S. Clark and S. Martinez-Nunez, “Another Cluster of Red Supergiants Close to RSGC1,” Astronomy & Astrophysics (A&A), Vol. 513, 2010, p. 74. doi:10.1051/0004-6361/200913373

[7]   B. Davies, D. de La Fuente, F. Najarro and J. A. Hinton, “A Newly Discovered Young Massive Star Cluster at the Far End of the Galactic Bar,” Mathematics & Physical Sciences, Vol. 419, No. 3, 2012, pp. 1860-1870. doi:10.1111/j.1365-2966.2011.19840.x

[8]   M. F. Skrutskie, R. M. Cutri, R. Stiening, M. D. Weinberg, S. Schneider, J. M. Carpenter, C. Beichman and R. Capps, “The Two Micron All Sky Survey (2MASS),” The Astrophysical Journal, Vol. 131, No. 2, 2006, pp. 1163-1183. doi:10.1086/498708

[9]   J. S. Mathis, “Interstellar Dust and Extinction,” Astronomy and Astrophysics, Vol. 28, 1990, pp. 37-70. doi:10.1146/annurev.aa.28.090190.000345

[10]   W. S. Dias, B. S. Alessi, A. Moitinho and J. R. D. Lepine, “New Catalogue of Optically Visible Open Clusters and Candidates,” Astronomy & Astrophysics (A&A), Vol. 389, 2002, pp. 871-873. doi:10.1051/0004-6361:20020668

[11]   D. Froebrich, A. Scholz and C. L. Raftery, “A Systematic Survey for Infrared Star Clusters with |b|<20? Using 2MASS,” Mathematics & Physical Sciences, Vol. 374, No. 2, 2007, pp. 399-408. doi:10.1111/j.1365-2966.2006.11148.x

[12]   C. Gonzalez-Fernandez and I. Negueruela, “A Third Cluster of Red Supergiants in the Vicinity of the Massive Cluster RSGC3,” Astronomy & Astrophysics (A&A), Vol. 539, 2012, p. 100. doi:10.1051/0004-6361/201118090

[13]   C. M. Dutra and E. Bica, “New Star Clusters Projected Close to the Galactic Centre,” Astronomy & Astrophysics (A&A), Vol. 359, 2000, pp. 9-12.

[14]   C. M. Dutra, S. Ortolani, E. Bica, B. Barbuy, M. Zoccali and Y. Momany, “NTT Infrared Imaging of Star Cluster Candidates towards the Central Parts of the Galaxy,” Astronomy & Astrophysics (A&A), Vol. 408, 2003, pp. 127-134. doi:10.1051/0004-6361:20030944

[15]   A. F. J. Moffat and N. Vogt, “Southern Open Star Clusters VI. UBV-Hbeta Photometry of 18 Clusters from Centaurus to Sagittarius,” Astronomy and Astrophysics, Vol. 20, 1975, pp. 155-182.

[16]   B. E. Westerlund, “Photometry and Spectroscopy of Stars in the Region of a Highly Reddened Cluster in ARA,” Astronomy and Astrophysics, Vol. 70, No. 3, 1987, pp. 311-324.

[17]   A. Lawrence, S. J. Warren, O. Almaini, A. C. Edge, N. C. Hambly, R. F. Jameson, P. W. Lucas, M. E. Casali, et al., “The UKIRT Infrared Deep Sky Survey (UKIDSS),” Mathematics & Physical Sciences, Vol. 379, No. 4, 2007, pp. 1599-1617. doi:10.1111/j.1365-2966.2007.12040.x

[18]   P. W. Lucas, M. G. Hoare, A. Longmore, A. C. Schroder, C. J. Davis, A. Adamson, R. M. Bandyopadhyay, R. de Grijs, et al., “The UKIDSS Galactic Plane Survey,” Mathematics & Physical Sciences, Vol. 391, No. 1, 2008, pp. 136-163. doi:10.1111/j.1365-2966.2008.13924.x

[19]   D. Minniti, P. W. Lucas, J. P. Emerson, R. K. Saito, M. Hempel, P. Pietrukowicz, A. V. Ahumada, M. V. Alonso, J. Alonso-Garcia, et al., “VISTA Variables in the Via Lactea (VVV): The Public ESO Near-IR Variability Survey of the Milky Way,” New Astronomy, Vol. 15, No. 5, 2010, pp. 433-443. doi:10.1016/j.newast.2009.12.002

[20]   R. K. Saito, M. Hempel, D. Minniti, P. W. Lucas, M. Rejkuba, I. Toledo, O. A. Gonzalez, J. Alonso-Garcia, et al., “VVV DR1: The First Data Release of the Milky Way Bulge and Southern Plane from the Near-Infrared ESO Public Survey VISTA Variables in the Via Lactea,” Astronomy & Astrophysics (A&A), Vol. 537, 2012, p. 107. doi:10.1051/0004-6361/201118407

[21]   C. Bonatto and E. Bica, “Open Clusters in Dense Fields: The Importance of Field-Star Decontamination for NGC 5715, Lynga 4, Lynga 9, Trumpler 23, Trumpler 26 and Czernik 37,” Mathematics & Physical Sciences, Vol. 377, No. 3, 2007, pp. 1301-1323. doi:10.1111/j.1365-2966.2007.11691.x

[22]   D. Froebrich, S. Schmeja, D. Samuel and P. W. Lucas, “Old Star Clusters in the FSR Catalogue,” Mathematics & Physical Sciences, Vol. 409, No. 3, 2010, pp. 1281-1288. doi:10.1111/j.1365-2966.2010.17390.x

[23]   T. Lejeune and D. Schaerer, “Database of Geneva Stellar Evolution Tracks and Isochrones for (UBV)_{J}(RI)_{C} JHKLL’M, HST-WFPC2, Geneva and Washington Photometric Systems,” Astronomy & Astrophysics (A&A), Vol. 366, 2001, pp. 538-546. doi:10.1051/0004-6361:20000214

[24]   E. P. Mercer, D. P. Clemens, M. R. Meade, B. L. Babler, R. Indebetouw, B. A. Whitney, C. Watson and M. G. Wolfire, “New Star Clusters Discovered in the GLIMPSE Survey,” The Astrophysical Journal, Vol. 635, No. 1, 2005, pp. 560-569. doi:10.1086/497260

[25]   J. Borissova, C. Bonatto, R. Kurtev, J. R. A. Clarke, F. Penaloza, S. E. Sale, D. Minniti, J. Alonso-Garcia, et al., “New Galactic Star Clusters Discovered in the VVV Survey,” Astronomy & Astrophysics (A&A), Vol. 532, 2011, p. 131. doi:10.1051/0004-6361/201116662

[26]   A. N. Chene, J. Borissova, J. R. A. Clarke, C. Bonatto, D. J. Majaess, C. Moni Bidin, S. E. Sale, F. Mauro, et al., “Massive Open Star Clusters Using the VVV Survey I. Presentation of the Data and Description of the Approach,” Astronomy & Astrophysics (A&A), Vol. 545, 2012, p. 54. doi:10.1051/0004-6361/201219064

[27]   R. Indebetouw, J. S. Mathis, B. L. Babler, M. R. Meade, C. Watson, B. A. Whitney, M. J. Wolff and M. G. Wolfire, “The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0 m Using GLIMPSE Data,” The Astrophysical Journal, Vol. 619, No. 2, 2005, pp. 931-938. doi:10.1086/426679

[28]   J. J. Stead and M. G. Hoare, “The Slope of the Near-Infrared Extinction Law,” MNRAS, Vol. 400, No. 2, 2009, pp. 731-742. doi:10.1111/j.1365-2966.2009.15530.x