CDROM/APJS/V99/P551 Massive Stars in M33 and M31 (Hunter+ 1995) ================================================================================ The Massive Star Populations in Ionized Gas Shells in M33 and M31 Deidre A. Hunter, Danielle M. Boyd, & Walter N. Hawley <1995, ApJS, 99, 551> =1995ApJS...99..551H ================================================================================ Abstract: We present BVI photometry of the massive stars in and around five Halpha shells in M33 and two in M31. These data can be used to statistically compare the stellar population with ionization and formation requirements of the gas shell. We have counted the numbers of massive stars encircled by the shells and embedded within the gaseous structures and corrected these numbers statistically for background and foreground interlopers. We find that the stellar production exceeds the ionization requirements of the nebulae by factors of 4-10. Thus, it is reasonable that the shells are photoionized and that a large fraction of the ionizing photons escape into the rest of the galaxy. We have also compared the number of massive stars counted and extrapolated to 7 Msun with the number required to form the shells according to a simple formation model. With one exception, we find that the number of stars estimated to be present exceeds the number required by the model for our assumptions of age and ambient gas density. This comparison and the morphology evident in Halpha images suggests that the modification of the interstellar medium by the massive stars in these regions has been far more complicated than is currently considered in formation models. There is evidence for multiple, and to some extent discreet, events in the production of the gas structures. A more detailed modeling will be necessary to adequately account for the stellar populations and Halpha morphology. Keywords: galaxies: individual (M31, M33) -- galaxies: ISM -- galaxies: star clusters -- galaxies: stellar content -- stars: early-type File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table2.dat 71 2228 The photometry table3.dat 47 24 The groups and reddening -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 A9 --- Region The region in M33 or M31 10 I1 --- Group *Group identification number within region 11-13 I3 --- Star Star identification number within the group 14-21 F8.2 pix X *X pixel coordinate 22-29 F8.2 pix Y *Y pixel coordinate 30-36 F7.2 mag V V magnitude 37-43 F7.2 mag e_V Uncertainty in V 44-50 F7.2 mag B-V *[]?=100.00 B-V color 51-57 F7.2 mag e_B-V *[]?=100.00 Uncertainty in B-V color 58-64 F7.2 mag V-I *[]?=100.00 V-I color 65-71 F7.2 mag e_V-I *[]?=100.00 Uncertainty in V-I color -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- Group: See Table 3 for descriptions of the groups. X, Y: The X,Y pixel coordinates are relative to the long V-band image shown in figure 1 (plates 11-16) of the printed paper. B-V, e_B-V, V-I, e_V-I: A magnitude of 100.00 indicates that the star was not measured through that filter. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 A9 --- Region The region in M33 or M31 10 I1 --- Group Group identification number within region 11-12 2X --- --- Blank 13-42 A30 --- Comment Comment on the group 43-47 F5.2 --- E(B-V) []? Reddening -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 31-Aug-95