CDROM/AJ/V109/P1055 Globulars of M81 (Perelmuter & Racine 1995) ================================================================================ The Globular Cluster System of M81 Jean-Marc Perelmuter & Rene Racine <1995, AJ, 109, 1055> =1995AJ....109.1055P ================================================================================ Abstract: We have obtained photometric BVR, morphological, and astrometric information on 3774 objects located within a 25' radius of M81. This catalogue is complete for 15 <= V <= 21; it is used here to identify globular cluster candidates in M81 and as a database for a statistical analysis of the system as a whole. The M81 globular cluster system is revealed as a strong surface density excess of ~70 objects within an 11 kpc galactocentric radius. The total population is estimated at N_T = 210 +/- 30 globulars. The spatial, (B-V), and (V-R) distributions are very similar to those of the Milky Way and of M31. Small but significant systematic errors in Madore et al.'s [AJ, 106, 2243 (1993)] photometry could be responsible for an overestimate of the Cepheid distance to M81 [(m-M)0 = 27.8] and we propose a revised modulus of (m-M)0 = 27.5 +/- 0.3. The globular cluster luminosity function then reaches its maximum at M_V* = -7.5 +/- 0.4, as it does in the galaxy and in M31. There is suggestive evidence that 13 +/- 5 objects are globulars seen through the disk of M81; spectroscopy or high-resolution imaging will resolve this issue. Using the (B-R)0 index to trace [Fe/H], we notice a weak dependence of mean metallicity on galactocentric distance, as observed in the galaxy and in M31. This result argues in favor of in situ globular formation during the continuous collapse and self-enrichment of an early-type spiral host. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table6.dat 74 3774 Catalogue of objects in the M81 field -------------------------------------------------------------------------------- Byte-by-byte Description of file: table6.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 I5 --- ID Identification number 6 1X --- --- Blank 7- 9 I3 h RAh Right ascension (2000) 10-12 I3 min RAm R.A. 13-19 F7.3 s RAs R.A. 20 A1 --- DE- Declination (always blank) 21-22 I2 deg DEd Declination (2000) 23-25 I3 arcmin DEm Dec. 26-31 F6.2 arcsec DEs Dec. 32-38 F7.1 yr Epoch Mean epoch of observation 39-44 F6.2 mag V V magnitude 45-50 F6.2 mag B-V B-V color 51-56 F6.2 mag V-R V-R color 57-58 I2 --- N Number of plates object detected upon 59-63 I5 mas/yr PM_Glon Proper motion in galactic longitude 64-68 I5 mas/yr PM_Glat Proper motion in galactic latitude 69-74 F6.1 --- PM_Sig *Level of significance of total PM -------------------------------------------------------------------------------- Notes for file: table6.dat -------------------------------------------------------------------------------- PM_Sig: The level of significance of the total proper motion, mu/sig_mu, where mu = (PM_Glon^2 + PM_Glat^2)^(1/2) -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 03-May-1995