C.D.S. - SIMBAD4 rel 1.7 - 2020.12.03CET13:04:32

2012A&A...545A..43C - Astronomy and Astrophysics, volume 545A, 43-43 (2012/9-1)

Two-dimensional metallicity distribution of the ionized gas in NGC 628 and NGC 6946.


Abstract (from CDS):

We present here two H II region catalogues with azimuthal resolution for the two grand design galaxies NGC 628 and NGC 6946. With the help of these catalogues, we study several properties of the star-forming processes occurring in spiral galaxies. We obtained direct imaging in the narrow-band filters centred at Hα, Hβ, [OII]λ3727, and [OIII]λλ4959, 5007 and their respective continua. After the calibration and correction of the data, we obtained for each HII region the de-reddened fluxes in the aforementioned lines, the size, the Hα equivalent width, and, using two different empirical calibrations, the metallicity. Employing a method based on the Delaunay triangulation, a two-dimensional (2D) representation of the metallicity was obtained. Data for 209 H II regions of NGC 628 and 226 H II regions of NGC 6946 are obtained. The radial behaviours of the Hα equivalent width, the excitation, and the oxygen abundance are derived. Two-dimensional representations of the metallicity and the excitation are calculated for the galaxies in the study. The two empirical calibrations of the metallicity are compared. The behaviours of the extinction and the Hα equivalent width are similar to those presented in the literature. The oxygen abundance gradients obtained in this study agree with previously published values. However, more regions were examined than in previous studies. We find a difference of about 0.6dex between the two empirical calibrations employed. Finally, the 2D representations of the metallicity reveal high metallicity knots in NGC 628, and for NGC 6946 a high metallicity azimuthal structure is discovered. These high metallicity regions seem to be linked to the arms of the galaxies and are probably produced by an increase in the temperature of the ionizing clusters in the H II regions, which may be linked to variations in the initial mass functions of the galaxies between the arm and interarm regions.

Abstract Copyright:

Journal keyword(s): galaxies: spiral - HII regions - galaxies: abundances - galaxies: individual: NGC 628 - galaxies: individual: NGC 6946

VizieR on-line data: <Available at CDS (J/A+A/545/A43): table4.dat table5.dat table6.dat table7.dat table8.dat table9.dat>

Nomenclature: [CCB2012] NGC628 NNN,[CCB2012] NGC6946 NNN N=435

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 6

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Number of rows : 6

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 NGC 226 GiG 00 42 54.035 +32 34 51.60   14.4       ~ 30 0
2 [BKG99] NGC 628 7 HII 01 36 35.5 +15 50 11           ~ 18 0
3 M 74 G 01 36 41.772 +15 47 00.46 10.52 10.00 9.46 9.16   ~ 1437 1
4 NGC 4395 Sy2 12 25 48.8639154223 +33 32 48.694684028 10.84 10.54 10.11 9.98   ~ 1015 1
5 M 101 GiP 14 03 12.583 +54 20 55.50   8.46 7.86 7.76   ~ 2579 2
6 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2268 2

    Equat.    Gal    SGal    Ecl

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