CDROM/AJ/V108/P1276 Clusters in GEHRs (Mayya 1994) ================================================================================ Embedded Clusters in Giant Extragalactic HII Regions. I. BVRHalpha Photometry Y. D. Mayya <1994, AJ, 108, 1276> =1994AJ....108.1276M ================================================================================ Abstract: Photometry in BVR continuum bands and in the emission line of Halpha+ [N II] are presented for a sample of H II complexes in disk, spiral arm and nuclear regions of galaxies NGC 1365, 1566, 2366, 2903, 2997, 3351, 4303, 4449, and 5253. Main sources of errors on H II region photometry are discussed. Errors due to background subtraction are parametrized in terms of background nonuniformity and fractional background contribution and are described separately in the Appendix. Our photometric data are compared with the existing data in the literature. Photometric properties of the sample regions are analyzed statistically and its implications on star formation are briefly discussed. Colors and Halpha+[N II] equivalent widths of nuclear H II regions are found to be distinctly different from disk H II regions, suggesting different star formation histories. We have identified a few high Halpha+[N II] equivalent width regions, which are fainter than average in both emission line and continuum fluxes, thus accounting for the low frequency of occurence of such regions in flux limited samples. Description: Table 3 is presented in its entirety in the file table3.txt. The format of this table did not follow the normal standard for easy transformation to FITS format, so the data for each galaxy were written to individual files. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table3.txt 80 286 Photometric catalogue of H II regions n1365.dat 80 16 Table 3 data for NGC 1365 n1566.dat 80 12 Table 3 data for NGC 1566 n2366.dat 80 3 Table 3 data for NGC 2366 n2903.dat 80 18 Table 3 data for NGC 2903 n2997ne.dat 80 36 Table 3 data for NGC 2997-NE n2997neg.dat 80 9 Table 3 data for NGC 2997-NE (Groups) n2997sw.dat 80 15 Table 3 data for NGC 2997-SW n3351.dat 80 7 Table 3 data for NGC 3351 n4303.dat 80 40 Table 3 data for NGC 4303 n4303g.dat 80 16 Table 3 data for NGC 4303 (Groups) n4449.dat 80 12 Table 3 data for NGC 4449 n5253.dat 80 2 Table 3 data for NGC 5253 -------------------------------------------------------------------------------- Byte-by-byte Description of files: n1365.dat n1566.dat n2366.dat n2903.dat n2997ne.dat n2997neg.dat n2997sw.dat n3351.dat n4303.dat n4303g.dat n4449.dat n5253.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 --- ID *H II region numbers 3 1X --- --- Blank 4- 7 I4 --- X *X pixel coordinate 8-11 I4 --- Y *Y pixel coordinate 12-13 2X --- --- Blank 14 A1 --- RA_dir *[EW] Direction of RA position 15-17 I3 arcsec RA *[]? Approximate right ascension position 18 1X --- --- Blank 19 A1 --- DE_dir *[NS] Direction of DE position 20-22 I3 arcsec DE *[]? Approximate declination position 23-28 F6.1 arcsec Diam Diam. of aperture for mag. extractions 29 1X --- --- Blank 30 A1 --- l_V [> ] Limiting character for V 31-35 F5.2 mag V *V magnitude 36-41 F6.2 mag B-V *[]? B-V color 42-47 F6.2 mag V-R *[]? V-R color 48-55 F8.2 mW/m2 F_alpha Log of observed H_alpha+[N II] flux 56 1X --- --- Blank 57 A1 --- l_W(Ha) Limiting character for W(Ha) 58-61 I4 0.1nm W(Ha) *Emission equivalent width 62-64 I3 --- Qual *Index of photometric quality 65-66 2X --- --- Blank 67-80 A14 --- Other_ID *Id. from other authors when available. -------------------------------------------------------------------------------- Notes for file: n1365.dat n1566.dat n2366.dat n2903.dat n2997ne.dat n2997neg.dat n2997sw.dat n3351.dat n4303.dat n4303g.dat n4449.dat n5253.dat -------------------------------------------------------------------------------- ID: H II region numbers as identified on the charts in the printed paper. X, Y: X and Y pixel coordinates on the aligned CCD images, which are the same as that appearing on the grid around identification charts. For NGC 4449 the grids contain different pixel numbers than that given in these columns for the reasons mentioned in the text. RA_dir, RA, DE_dir, DE: Approximate position of the H II region, along Right Ascension and declination in seconds of arc, with respect to the galactic nucleus. These were obtained by transforming X and Y assuming that the RA-DEC axis is aligned with X-Y axis of the CCD. Since the alignment during observations is only approximate (<= 5 deg), RA and DEC values away from the center are less accurate, compared to those near the center of the CCD. Thus the positions should be used only for identification purposes. E, W, N, and S preceeding the numbers indicate respectively whether the H II region is to the east, west, north or south of the nucleus of the galaxy. V, B-V, V-R: V Magnitude, B-V and V-R colors of H II regions after subtracting assumed background. The rms errors on the measured magnitudes are in the range 0.05--0.10, as estimated from measurements on multiple frames. W(Ha): H_alpha + [N II] emission equivalent width in Ang with R magnitude as an estimate for the continuum at H_alpha, computed using the equation W(Ha) = 1.633E-11*F_alpha/10**(-0.4(R+48.6)) where, F_alpha is the H_alpha + [N II] flux in mW/m^2 (erg/s/cm^2). The measurement errors are < 20 Ang. Note that the R band magnitudes used in the above definition include emission from the nebular continuum and lines. Qual: An index of photometric quality. It is an integer between 1 and 4 and gives a measure of the background domination for BVR measurements. Higher the index, more sensitive are the colors to the background measurement. See printed paper for details. Other_ID: Identification from other authors when available. For measurements with bigger apertures, individual GEHRs enclosed within the aperture are indicated. The notations used for identifications are: CM Crillon and Monnet 1969, A&A, 1, 449 HK Hodge and Kennicutt 1983, AJ, 88, 296 HP Hawley and Phillips 1980, AJ, 235, 783 AN Alloin and Nieto 1982, A&AS, 50, 491 Oka Oka et. al 1974, PASJ, 26, 289 Tpp Prabhu 1980, ApSpSci., 68, 519 L Lindblad, P.O. see Alloin et. al 1981, A&A, 101, 377 M McCall, Rybski, and Shields 1985, ApJS, 57, 1 RW Roy and Walsh 1986, MNRAS, 223, 39; 1987, MNRAS, 228, 883; 1988, MNRAS, 234, 977 WR Walsh and Roy 1989a, MNRAS, 239, 297; 1989b, ApJ, 341, 722 -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 31-Oct-1994