CDROM/AJ/V109/P2503 Embedded Clusters. II. (Mayya 1995) ================================================================================ Embedded Clusters in Giant Extragalactic H II Regions. II. Evolutionary Population Synthesis Model Y.D. Mayya <1995, AJ, 109, 2503> =1995AJ....109.2503M ================================================================================ Abstract: A stellar population synthesis model, suitable for comparison with Giant Extragalactic H II Regions (GEHRs), is constructed incorporating the recent developments in modeling stellar evolution by Maeder and co-workers and stellar atmospheres by Kurucz. A number of quantities suitable for comparison with broadband data of GEHRs in visible and near-infrared parts of the spectrum are synthesized in addition to the hydrogen and helium ionizing photon production rates at solar metallicities, for three scenarios of star formation -- (i) instantaneous burst (IB); (ii) continuous star formation (CSF); and (iii) two bursts of star formation, with the older burst rich in red supergiants. For the IB case, evolution of colors shows three distinct phases -- an initial steady blue phase, followed by a red bump (5-15 Myr) and another steady phase with colors intermediate to the earlier two phases. CSF colors asymptotically reach peak values at ~10 Myr, never reaching the reddest IB colors. Ionizing photon production rate falls off by an order of magnitude in 6 Myr for IB, whereas it almost remains constant for the CSF model. Two-burst models with burst separations ~10 Myr have properties of both IB and CSF, simultaneously producing the red IB colors and high ionizing photon rate, making such regions easily distinguishable using optical observations. Flat IMFs result in bluest colors when the massive stars are on the main sequence and reddest colors during the red supergiant phase of the evolving massive stars. Errors on the computed quantities due to the statistical uncertainties inherent in the process of star formation become negligible for cluster masses in excess of 10^5 Msun. Our GEHR spectra in the range 200 nm to 3 um are found to be in good agreement with the computations of Mas-Hesse & Kunth (1991, A&AS, 88, 399). Description: Tables 3, 4, and 5 are given. Each table has been split into three parts, a, b, and c, where each part includes derived quantities for Initial Mass Functions (IMF) defined by slope, lower cutoff (M_l), and upper cutoff (M_u), as follows: part a: slope = 2.5, M_l = 1, M_u = 60 part b: slope = 3.5, M_l = 1, M_u = 30 part c: slope = 1.0, M_l = 1, M_u = 120 Tabulated quantities are smoothed over a period of 0.5 Myr to suppress the short term fluctuations on the computer quantities. For the continuous star-formation model, constant star-formation rate (SFR) is assumed in computations of the tabulated quantities. Table 5 give the ages of the young and old bursts for the two-burst models. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table3a.dat 97 41 Derived quantities for star clusters with IB table3b.dat 97 41 Derived quantities for star clusters with IB table3c.dat 97 41 Derived quantities for star clusters with IB table4a.dat 97 41 Derived quantities for star clusters with CSF table4b.dat 97 41 Derived quantities for star clusters with CSF table4c.dat 97 41 Derived quantities for star clusters with CSF table5a.dat 97 68 Der. quantities for star clusters w/ two bursts table5b.dat 97 68 Der. quantities for star clusters w/ two bursts table5c.dat 97 68 Der. quantities for star clusters w/ two bursts -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3a.dat table3b.dat table3c.dat table4a.dat table4b.dat table4c.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 F5.2 Myr Age Age of the cluster 6-12 F7.2 Msun/Lsun M/L Ratio of total mass to bolometric lum. 13-19 F7.2 Msun/Lsun M/Lv Ratio of total mass to visual luminosity 20-26 F7.2 --- N_L Lyman continuum photon production rate per unit mass of the cluster 27-33 F7.2 --- fHe Fraction of hydrogen ionizing photons which are capable of ionizing helium 34-40 F7.2 --- Phi/Lb *Ratio of expected Hbeta to blue band lum. 41-47 F7.2 mag B-V B-V color 48-54 F7.2 mag V-R V-R color 55-61 F7.2 mag V-I V-I color 62-68 F7.2 mag J-H J-H color 69-75 F7.2 mag H-K H-K color 76-82 F7.2 mag V-K V-K color 83-89 F7.2 0.1nm W_Hb *Hbeta equivalent width 90-97 F8.2 0.1nm W_Ha *Halpha equivalent width -------------------------------------------------------------------------------- Notes for file: table3a.dat table3b.dat table3c.dat table4a.dat table4b.dat table4c.dat -------------------------------------------------------------------------------- Phi/Lb: Lyman continuum photon rate N_L is also expressed in units or expected Hbeta luminosity Phi from a nebula at 10,000 K, and defined as: Phi = 4.78 x 10^-13 N_L. Phi in this equation has dimensions or erg/s/Msun, and N_L in ph/s/Msun. W_Hb, W_Ha: Equivalent widths assuming a gas temperature of 10,000 K. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5a.dat table5b.dat table5c.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 F5.2 Myr T_yng Age of the younger burst 6-12 F7.2 Myr T_old Age of the older burst 13-19 F7.2 Msun/Lsun M/L Ratio of total mass to bolometric lum. 20-26 F7.2 Msun/Lsun M/Lv Ratio of total mass to visual luminosity 27-33 F7.2 --- N_L Lyman continuum photon production rate per unit mass of the cluster 34-40 F7.2 --- fHe Fraction of hydrogen ionizing photons which are capable of ionizing helium 41-47 F7.2 --- Phi/Lb *Ratio of expected Hbeta to blue band lum. 48-54 F7.2 mag B-V B-V color 55-61 F7.2 mag V-R V-R color 62-68 F7.2 mag V-I V-I color 69-75 F7.2 mag J-H J-H color 76-82 F7.2 mag H-K H-K color 83-89 F7.2 mag V-K V-K color 90-96 F7.2 0.1nm W_Hb *Hbeta emission line equivalent width 97-104 F8.2 0.1nm W_Ha *Halpha emission line equivalent width -------------------------------------------------------------------------------- Notes for file: table5a.dat table5b.dat table5c.dat -------------------------------------------------------------------------------- Phi/Lb: Lyman continuum photon rate N_L is also expressed in units or expected Hbeta luminosity Phi from a nebula at 10,000 K, and defined as: Phi = 4.78 x 10^-13 N_L. Phi in this equation has dimensions or erg/s/Msun, and N_L in ph/s/Msun. W_Hb, W_Ha: Equivalent widths assuming a gas temperature of 10,000 K. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 19-Jul-1995