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J/AJ/116/2246   HII regions in UGCA 86, 92, 105 and UGC 4115 (Kingsburgh+, 1998)

Automatic determination of unbiased luminosity functions for H II regions. II. Four nearby dwarf galaxies. Kingsburgh R.L., McCall M.L. <Astron. J. 116, 2246 (1998)> =1998AJ....116.2246K (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Galaxies, spectra Keywords: galaxies: individual (UGCA 86, UGCA 92, UGCA 105, UGC 4115 - galaxies: ISM Abstract: Luminosity functions in Hα have been measured for H II regions in the four dwarf galaxies UGCA 86, UGCA 92, UGCA 105, and UGC 4115 using both the traditional flux measurement method of fixed-threshold photometry (FTP) and the new method, percentage-of-peak photometry (PPP). The UGCA galaxies are members of the IC 342-Maffei 1 group. These two methods give significantly different results in galaxies in which significant numbers of peaks are associated with H II region complexes. The work demonstrates that fluxes from FTP can lead to biased luminosity functions and that PPP should, in general, be preferred. It is also shown that PPP luminosity functions are not very sensitive to atmospheric transparency, whereas those constructed from FTP can be, based on data taken under different atmospheric conditions. Results to date for six galaxies show that spirals and dwarfs have luminosity functions of similar shape, which implies that the distribution of the masses of star formation sites is largely independent of the mass, and by implication, the metallicity, of the host galaxy. As measured by PPP, the mean surface brightness of the lower luminosity H II regions grows as the one-third power of the flux grows, exactly as predicted for an ensemble in which the gas density does not vary systematically with the mass of the star cluster. For the brightest H II regions, however, the relation steepens, which implies that the most massive star clusters are formed out of the densest clouds. Objects: ------------------------------------------------------------ RA (2000) DE GLON GLAT Designation(s) ------------------------------------------------------------ 03 59.8 +67 08 139.8 +10.6 UGCA 86 04 32.0 +63 36 144.7 +13.7 UGCA 92 05 14.3 +62 34 148.5 +13.7 UGCA 105 07 57.0 +14 24 207.0 +20.9 UGC 4115 ------------------------------------------------------------ File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 59 65 HII regions in UGCA 86 table4.dat 59 16 HII regions in UGCA 92 table5.dat 59 85 HII regions in UGCA 105 table6.dat 59 17 HII regions in UGC 4115
Byte-by-byte Description of file: table*.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Galaxy Galaxy name 11- 12 I2 --- [KM98] HII region number in the galaxy (1) 14- 16 I3 --- [HM95] ? Hodge & Miller (1995ApJ...451..176H) number 18- 19 I2 --- [HM95]2 ? Second Hodge & Miller (1995ApJ...451..176H) number 22- 27 F6.1 arcsec oRA Offset east from reference star (2) 29- 34 F6.1 arcsec oDE Offset north from reference star (2) 36- 38 F3.1 arcsec RadiusPPP ? Radius of circle covering same area as HII region from PPP (3) 40- 44 F5.2 --- logFluxPPP ? logarithm of total PPP flux relative to PPP values for HII reference region (3) 46- 49 F4.1 arcsec RadiusFTP ? Radius of circle covering same area as HII region from FTP (3) 51- 55 F5.2 --- logFluxFTP ? logarithm of total FTP flux relative to PPP values for HII reference region (3)
Note (1): [KM98] UGCA NNNN NN in Simbad Note (2): UGCA 86: reference star: GSC 4076-0876 UGCA 92: reference star: GSC 4069-1252 (see "History" section) UGCA 105: reference star: GSC 4084-2331 (see "History" section) UGC 4115: reference star: GSC 0792-0287 (see "History" section) Note (3): PPP: percentage-of-peak photometry FTP: fixed-threshold photometry UGCA 86: reference region: UGCA 86 61 UGCA 92: reference region: UGCA 92 15 UGCA 105: reference region: UGCA 105 16 UGC 4115: reference region: UGC 4115 14
Table 7: Positions and magnitudes of reference stars (GSC numbers correctedm see "History" section below) ------------------------------------------------------- Galaxy GSC number RA (2000.0) DE Vmag ------------------------------------------------------- UGCA 86 4076-0876 04 00 01.7 +67 09 11.9 14.06 UGCA 92 4069-1252 04 32 04.5 +63 37 22.4 13.96 UGCA 105 4084-2331 05 14 04.9 +62 36 15.2 15.00 UGC 4115 0792-0287 07 56 41.7 +14 20 31.5 8.16 History: From AJ electronic version * 07-May-1999: The GSC numbers of the reference stars were corrected 4069-1522 corrected to 4069-1252, 4084-2577 corrected to 4084-2331, and 0792-0729 corrected to 0792-0287. References: McCall et al., Paper I. 1996AJ....112.1096M
(End) James Marcout, Patricia Bauer [CDS] 19-Jan-1999
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