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 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:
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RA (2000) DE Designation(s)
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01 36 41.8 +15 47 00 NGC 628 = M74
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File Summary:
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FileName Lrecl Records Explanations
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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
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See also:
VII/20 : Catalogue of HII Regions (Sharpless 1959)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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
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Note (1): Position relative to the galactic center.
East is positive and North is positive.
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History: From AJ electronic version
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 25-Sep-2000