CDROM/AJ/V114/P0198 The Monoceros R2 Cluster (Carpenter+ 1997) ================================================================================ Properties of the Monoceros R2 Stellar Cluster John M. Carpenter, Michael R. Meyer, Catherine Dougados, Stephen E. Strom, and Lynne A. Hillenbrand <1997, AJ, 114, 198> =1997AJ....114..198C ================================================================================ Abstract: We present an extensive study of the stellar population of an embedded cluster in the MonR2 molecular cloud based upon a wide field (~15' x 15') J, H, and K band mosaic, deep near-infrared imaging at J, H, K, and nbL' bands of the central cluster region, and spectroscopic observations of 34 stars. By comparing the properties of the MonR2 cluster with other star forming regions, we ultimately hope to learn how the properties and formation of stars of various masses are related to the local physical conditions. The K band star counts indicate that the MonR2 cluster extends over a ~1.1 pc x 2.1 pc area with a FWHM cluster size of ~0.38 pc. Within this region the cluster contains ~309 stars brighter than m_K = 14.5m and >~ 475 stars over all magnitudes with a central stellar volume density of ~9000 stars pc^{-3}. We have further explored the properties of the cluster by using the spectroscopic and photometric data to construct an extinction-limited sample of 115 stars in the central 0.77 pc x 0.77 pc region of the cluster that is designed to contain all stars with A_V <= 11.3m and stellar masses >= 0.1 Msun. As a lower limit, 62% of the stars in this sample contain a near-infrared excess at K and/or L band. The K band excess fraction may be as high as 72% if the accretion characteristics of the stars in the MonR2 cluster are similar to stars in Taurus-Auriga. An initial reconnaissance of the stellar mass function suggests that the ratio of high to low mass stars in the extinction-limited sample is consistent with the value expected for a Miller-Scalo IMF. We do not find compelling evidence for mass segregation in the extinction-limited sample for stellar masses <~ 2 Msun, although the most massive star (~10 Msun) in the cluster appears to be forming near the cluster center. The properties of the MonR2 cluster are similar to other rich young clusters in the solar neighborhood, such as NGC 2024 and the Trapezium. (c) 1997 American Astronomical Society. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 62 512 SQIID Photometry of MonR2 table2.dat 83 390 IRCAM3 Photometry of MonR2 table1.tex 97 554 AASTeX version of table1.dat table2.tex 115 456 AASTeX version of table2.dat -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- ID ID number 5- 6 I2 h RAh Right ascension (1950) 7 1X --- --- Always ':' 8- 9 I2 min RAm R.A. 10 1X --- --- Always ':' 11-15 F5.2 s RAs R.A. 16 1X --- --- Blank 17 A1 --- DE- Declination sign 18 I1 deg DEd Declination (1950) 19 1X --- --- Always ':' 20-21 I2 arcmin DEm Dec. 22 1X --- --- Always ':' 23-26 F4.1 arcsec DEs Dec. 27-33 F7.2 mag J []? J band magnitude 34-38 F5.2 mag e_J []? 1-sigma uncertainty in J 39-45 F7.2 mag H []? H band magnitude 46-50 F5.2 mag e_H []? 1-sigma uncertainty in H 51-57 F7.2 mag K []? K band magnitude 58-62 F5.2 mag e_K []? 1-sigma uncertainty in K -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- ID ID number 4- 5 I2 h RAh Right ascension (1950) 6 1X --- --- Always ':' 7- 8 I2 min RAm R.A. 9 1X --- --- Always ':' 10-14 F5.2 s RAs R.A. 15 1X --- --- Blank 16 A1 --- DE- Declination sign 17 I1 deg DEd Declination (1950) 18 1X --- --- Always ':' 19-20 I2 arcmin DEm Dec. 21 1X --- --- Always ':' 22-25 F4.1 arcsec DEs Dec. 26-32 F7.2 mag J []? J band magnitude 33-37 F5.2 mag e_J []? 1-sigma uncertainty in J 38-44 F7.2 mag H []? H band magnitude 45-49 F5.2 mag e_H []? 1-sigma uncertainty in H 50-56 F7.2 mag K []? K band magnitude 57-61 F5.2 mag e_K []? 1-sigma uncertainty in K 62-68 F7.2 mag nbL []? nbL' band magnitude 69-73 F5.2 mag e_K []? 1-sigma uncertainty in nbL 74-83 A10 --- Notes *Additional notes -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- Notes: Cross identifications are from Beckwith et al. (1976) and Howard et al. (1994). An asterisk in this column indicates an additional note as listed below: 104 -- Stellar ? 122 -- Non-stellar at H; stellar and nebular components at K and nbL' 124 -- Extended at H and K; likely unresolved stars 129 -- Extended at H and K 151 -- Near IRS5; stellar at J and H; non-stellar at K and nbL' 156 -- Non-stellar 172 -- Non-stellar 193 -- Stellar at J? 214 -- Foreground star 233 -- Extended at H and K 235 -- Extended at K 252 -- Stellar? 254 -- Non-stellar at J and H; stellar and nebular components at K; stellar at nbL' 291 -- Saturated at K; photometry very uncertain in all bands 301 -- Non-stellar at J; stellar and nebulous at H; stellar at K and nbL' 315 -- Non-stellar 319 -- Detected at K, but photometry unreliable 364 -- Stellar with local nebulosity at H and K 372 -- Stellar with local nebulosity at JHK 374 -- Extended at all four bands; likely unresolved stars -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 26-Sep-1997