J/AJ/108/1276 J/AJ/108/1276 Clusters in GEHRs Y D Mayya Astron. J. 108 1276 1994 1994AJ....108.1276M Equivalent widths H II regions Photometry, H-alpha 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.

Gal Galaxies name (g for groups) --- ID H II region numbers number=1 H II region numbers as identified on the charts in the printed paper. --- Xpos X pixel coordinate number=2 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. pix Ypos Y coordinate number=2 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. pix dirRA Direction of RA position number=3 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 (<=5deg), 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. --- posRA Approximate right ascension position number=3 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 (<=5deg), 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. arcsec dirDE Direction of DE position number=3 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 (<=5deg), 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. --- posDE Approximate declination position number=3 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 (<=5deg), 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. arcsec Diam Diam. of aperture for mag. extractions arcsec l_Vmag Limiting character for V --- Vmag V magnitude number=4 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. mag B-V B-V color number=4 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. mag V-R V-R color number=4 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. mag Salpha Log of observed H_alpha+[N II] flux mW/m2 l_W(Ha) Limiting character for W(Ha) --- W(Ha) Emission equivalent width number=5 H_alpha + [N II] emission equivalent width in A 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 <20A. Note that the R band magnitudes used in the above definition include emission from the nebular continuum and lines. 0.1nm Qual Index of photometric quality number=6 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. --- OtherID Id. from other authors when available number=7 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, =1969A&A.....1..449C HK Hodge and Kennicutt 1983, =1983AJ.....88..296H HP Hawley and Phillips 1980, =1980ApJ...235..783H AN Alloin and Nieto 1982, =1982A&AS...50..491A Oka Oka et. al 1974, PASJ, 26, 289 Tpp Prabhu 1980, ApSpSci., 68, 519 L Lindblad, P.O. see Alloin et. al, 1981A&A...101..377A M McCall, Rybski, and Shields 1985, =1985ApJS...57....1M RW Roy and Walsh: 1986MNRAS.223...39R; 1987MNRAS.228..883R; 1988MNRAS.234..977R WR Walsh and Roy: 1989MNRAS.239..297W; 1989ApJ...341..722W -------------------------------------------------------------------------------- Acknowledgements: Mayya Y.D. ydm@tifrvax.tifr.res.in Indian Institute of Astrophysics, Bangalore 560 034, India AAS CD-ROM series, Volume 3, 1995 --- Lee Brotzman ADS 1994, Patricia Bauer [CDS] 16-Feb-1995Oct31 J_AJ_108_1276.xml