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J/ApJ/510/104     Ionizing Stars of Extragalactic H II Regions (Bresolin+ 1999)

The Ionizing Stars of Extragalactic H II Regions Bresolin F., Kennicutt R. C., Garnett D. R. <Astrophys. J. 510, 104 (1999)> =1999ApJ...510..104B
ADC_Keywords: Galaxies, optical; H II regions; Spectroscopy Keywords: galaxies: ISM - galaxies: spiral Abstract: Medium-resolution spectra from 3650 to 10000 Å are presented for 96 giant H II regions distributed in 20 spiral galaxies. In order to interpret the data, we have calculated two separate grids of photoionization models, adopting single-star atmospheres (Kurucz) and star clusters synthesized with different initial mass functions (IMFs) as ionizing sources. Additional models were computed with more recent non-LTE stellar atmospheres, in order to check the effects of different stellar ionizing fluxes. We use the radiation softness parameter η'=([O II]/[O III])/([S II]/[S III]) of Vilchez & Pagel (1988MNRAS.231..257V) to test for a metallicity dependence of the effective temperatures of the ionizing stars. Our results are consistent with a significant decrease in mean stellar temperatures of the ionizing stars with increasing metallicity. The magnitude of the effect, combined with the behavior of the He I λ5876/Hβ ratio, suggest a smaller upper mass limit for star formation at abundances higher than solar, even when considering the effects of metallicity on stellar evolution and atmospheric line blanketing. However, the exact magnitudes of the stellar temperature and IMF variations are dependent on the choice of stellar atmosphere and evolution models used, as well as on uncertainties in the nebular abundance scale at high metallicities. Our results also constrain the systematic behavior of the ionization parameter and the N/O ratio in extragalactic H II regions. The observed spectral sequences are inconsistent with current stellar evolution models, which predict a luminous, hot W-R stellar population in evolved H II regions older than 2-3 Myr. This suggests either that the hardness of the emitted Lyman continuum spectrum has been overestimated in the models or that some mechanism disrupts the H II regions before the W-R phases become important. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 108 96 Reddening-corrected line fluxes of HII regions
See also: J/A+AS/112/35 : Emission lines from giant HII regions (Garcia Vargas+, 1995) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name Galaxy name 13- 14 I2 --- Seq Galaxy sequence number 17- 21 I5 arcsec RAoff Right ascension offset from the galaxy nucleus 25- 29 I5 arcsec DEoff Declination offset from the galaxy nucleus 32- 35 I4 --- OII OII (3727AA) flux (1) 39- 40 I2 --- e_OII Uncertainty in OII 43- 46 I4 --- OIII OIII (5007+4959AA) flux (1) 49- 50 I2 --- e_OIII Uncertainty in OIII 53- 55 I3 --- HeI HeI (5876AA) flux (1) 59- 60 I2 --- e_HeI Uncertainty in HeI 63- 66 I4 --- NII NII (6548+6583AA) flux (1) 69- 70 I2 --- e_NII Uncertainty in NII 73- 75 I3 --- SII SII (6716+6731AA) flux (1) 79- 80 I2 --- e_SII Uncertainty in SII 85- 88 I4 --- SIII (9069+9532AA) flux (1) 91- 92 I2 --- e_SIII Uncertainty in SIII 94-108 A15 --- HIIName HII region names (2)
Note (1): Line fluxes given in units of Hβ = 100 Note (2): Names use the abbreviations: HK = Hodge & Kennicutt 1983, An Atlas of H II Regions in 125 Galaxies (PAPS Document ANJOA88-296-300) (New York: AIP Auxiliary Publication Service) H = Hodge 1976 (1976ApJ...205..728H) P = Pellet+ 1978 (1978A&AS...31..439P) CC = Carranza+ 1969 (1969A&A.....1..479C) GS = Garnett & Shields 1987 (1987ApJ...317...82G) D = Dufour+ 1980 (1980ApJ...236..119D)
History: * 07-Feb-2000: From ApJ electronic edition. * 15-Nov-2005: HII regions in NGC 3521 were erroneously attached to NGC 3368 References: McCall+ 1985 (1985ApJS...57....1M) Oey & Kennicutt 1993 (1993ApJ...411..137O) Zaritsky+ 1994 (1994ApJ...420...87Z)
(End) Greg Schwarz (AAS) 07-Feb-2000
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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