Inclination-Dependent Extinction Effects in Disk Galaxies in the Sloan Digital Sky Survey
Abstract
We analyze the r-band absolute magnitude and u - r color of low-redshift (z < 0.06) galaxies in the Sloan Digital Sky Survey Data Release 6. Galaxies with nearly exponential profiles (Sloan parameter fracDeV < 0.1) fall on the blue sequence of the color-magnitude diagram; if, in addition, these exponential galaxies have Mrlesssim - 19, they show a dependence of u - r color on apparent axis ratio q expected for a dusty disk galaxy. We create a subsample of bright exponential galaxies, with typical Hubble types Sbc and Sc; then, by comparing the normalized luminosity functions for galaxies with different values of q, we measure how the high-luminosity cutoff of the luminosity function depends on apparent axis ratio. In this way, we measure a dependence of dimming on apparent axis ratio well fit by the relation Δ Mr = 1.27(log q)2, rather than the Δ M propto log q law that is frequently assumed. When the absolute magnitudes of bright exponential galaxies are corrected to their "face-on" value, M fr = Mr - Δ Mr, the average u - r color is linearly dependent on M fr for a given value of q; the value of d(u - r)/dM fr ranges from ~0.10 for nearly face-on galaxies (q > 0.9) to ~0.26 for nearly edge-on galaxies (q < 0.3). When the dimming law Δ Mr propto (log q)2 is used to create an inclination-corrected sample of bright exponential galaxies, their apparent shapes are consistent with a distribution of mildly noncircular disks, with median short-to-long axis ratio γ ≈ 0.22 and median disk ellipticity epsilon ≈ 0.08.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2008
- DOI:
- 10.1086/591898
- arXiv:
- arXiv:0801.2400
- Bibcode:
- 2008ApJ...687..976U
- Keywords:
-
- galaxies: fundamental parameters;
- galaxies: photometry;
- galaxies: spiral;
- galaxies: statistics;
- Astrophysics
- E-Print:
- submitted to Ap.J