The Abundance Properties of Nearby Late-Type Galaxies. Ii. The Relation Between Abundance Distributions and Surface Brightness Profiles

Abstract

The relations between oxygen abundance and disk surface brightness (OH-SB relation) in the infrared W1 band are examined for nearby late-type galaxies. The oxygen abundances were presented in Paper I. The photometric characteristics of the disks are inferred here using photometric maps from the literature through bulge-disk decomposition. We find evidence that the OH-SB relation is not unique but depends on the galactocentric distance r (taken as a fraction of the optical radius R 25 ) and on the properties of a galaxy: the disk scale length h and the morphological T-type. We suggest a general, four-dimensional OH-SB relation with the values r, h, and T as parameters. The parametric OH-SB relation reproduces the observed data better than a simple, one-parameter relation; the deviations resulting when using our parametric relation are smaller by a factor of ∼1.4 than that of the simple relation. The influence of the parameters on the OH-SB relation varies with galactocentric distance. The influence of the T-type on the OH-SB relation is negligible at the centers of galaxies and increases with galactocentric distance. In contrast, the influence of the disk scale length on the OH-SB relation is at a maximum at the centers of galaxies and decreases with galactocentric distance, disappearing at the optical edges of galaxies. Two-dimensional relations can be used to reproduce the observed data at the optical edges of the disks and at the centers of the disks. The disk scale length should be used as a second parameter in the OH-SB relation at the center of the disk while the morphological T-type should be used as a second parameter in the relation at optical edge of the disk. The relations between oxygen abundance and disk surface brightness in the optical B and infrared K bands at the center of the disk and at optical edge of the disk are also considered. The general properties of the abundance-surface brightness relations are similar for the three considered bands B, K, and W1.

NGC 55: a disc galaxy with flat abundance gradients

“…The abundances are uniformly distributed in the radial direction. This agrees with the study of smaller samples of H ii regions (Webster & Smith 1983;Pilyugin et al 2014) and it is in qualitative agreement with the blue supergiant radial gradient (Kudritzki et al 2016). We investigate the origin of such flat gradient comparing NGC 55 with its companion galaxy, NGC 300, similar in terms of mass and luminosity and located in the same group of galaxies.…”

“…NGC 55 radial gradients of O/H and N/H have been also recently re-analysed from literature data by Pilyugin et al (2014). They found oxygen and nitrogen gradients essentially flat, and in good agreement with our results (see Table5 The comparison between the H ii region and blue supergiant populations is extremely interesting because they both are young populations and should trace the same epoch in the galaxy lifetime.…”

Radial distribution of dust, stars, gas, and star-formation rate in DustPedia face-on galaxies

“…In this table, column (1) gives the galaxy names, column (2) the metallicity gradients with uncertainty from Pilyugin et al (2014), column (3) the oxygen abundances at the radius of 0.7×r 25 that is equivalent to the solar radius in our Galaxy, columns (4) and (5) α CO values derived without and with the correction for metallicity gradient, respectively, and columns (6) and (7) mean α CO values derived from Sandstrom et al (2013) for the galaxies in common with our sample for the entire galaxies and the inner galactic kpc, respectively.…”

“…All galaxies of our sample are contained in Pilyugin et al (2014) and we used their metallicity values (see their Table 2) to study the variation of the CO-to-H 2 conversion factor as a function of O/H abundance (see Sects. 5.3 and 7).…”

“…1) NGC 3031 (M 81) is not listed in this table, although it has data both in atomic and molecular gas because its molecular gas profile is not fitted by an exponential function; 2) metallicity gradients from Pilyugin et al (2014); 3) derived oxygen abundances at the radius of 0.7 × r 25 ; 4) and 5) α CO values derived neglecting metallicity gradients and taking into account metallicity gradients following prescriptions given in Sect. 7; 6) and 7) α CO values derived from Sandstrom et al (2013) for the entire galaxy and the inner kpc of the galaxy, respectively.…”