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J/AJ/120/1306       NGC 628 H II regions                     (Lelievre+, 2000)

The H II regions of the extreme outer disk of NGC 628 Lelievre M., Roy J.R. <Astron. J. 120, 1306 (2000)> =2000AJ....120.1306L
ADC_Keywords: Galaxies, photometry ; H II regions ; Photometry, H-alpha Keywords: galaxies: individual (NGC 628) - galaxies: ISM - H II regions - stars: formation Abstract: Employing deep Hα narrowband imagery, we identified and measured the fluxes of 137 small H II regions in the extreme outer disk (R≥R25) of the nearly face-on, Sc I galaxy NGC 628. A majority of these H II regions are located in two faint, outer spiral arms visible in H I maps. The faintest H II regions that could be measured have fluxes of only a few times 10-16ergs/cm2/s, which correspond to luminosities of 1036ergs/s, or a fraction of the Orion Nebula luminosity. The most distant object detected is at R∼27kpc from the galaxy center. The massive star formation rate, as measured from the azimuthally averaged Hα flux, is consistent with a monotonic decrease as far as R∼1.3R25 (20kpc), where there is a sharp drop. The Schmidt law for the whole disk of NGC 628 corresponds to a relatively steep power law with n=2.9±0.2, but it "fails" below Σgas≤4M/pc2; the index depends strongly on the CO data used. We derived the luminosity function (LF) of 598 H II regions over the whole disk, and we compared the shapes of the cumulative LFs between R≥R25 and R<R25; the LF of the outer regions is significantly steeper than that of the inner regions. Objects: ----------------------------------------- RA (2000) DE Designation(s) ----------------------------------------- 01 36 41.8 +15 47 00 NGC 628 = M74 ----------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 59 142 Positions, galactocentric radii, fluxes, luminosities, and star formation rates of the H II regions at R≥R25
See also: VII/20 : Catalogue of HII Regions (Sharpless 1959) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 4 I4 arcsec EWPos H II region position (1) 7- 10 I4 arcsec NSPos H II region position (1) 13- 15 I3 arcsec GalRad H II galactocentric radius 17- 21 F5.1 10-16mW/m2 Flux H II region flux (10-16ergs/cm2/s) 24- 27 F4.1 10-16mW/m2 e_Flux Uncertainty in Flux 31- 35 F5.1 10+29W Lum H II region luminosity (1036ergs/s) 38- 41 F4.1 10+29W e_Lum Uncertainty in Lum 46- 50 F5.1 10-5solMass/yr SFR H II region star formation rate 53- 56 F4.1 10-5solMass/yr e_SFR Uncertainty in SFR
Note (1): Position relative to the galactic center. East is positive and North is positive.
History: From AJ electronic version
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 25-Sep-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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