The shapes of galaxies in the Sloan Digital Sky Survey

By N. Padilla, M. H. U. C. D. Chile, P. University. 2008

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We determine the underlying shapes of spiral and elliptical galaxies in the Sloan Digital Sky Survey Data Release 6 (SDSS DR6) from the observed distribution of projected galaxy shapes, taking into account the effects of dust extinction and reddening. We assume that the underlying shapes of spirals and ellipticals are well approximated by triaxial ellipsoids. The elliptical galaxy data are consistent with oblate spheroids, with a correlation between luminosity and ellipticity: the mean values of minor to middle axis ratios are 0.41 ± 0.03 for M r ≈-18 ellipticals and 0.76 ± 0.04 for M r ≈-22.5 ellipticals. Ellipticals show almost no dependence of axial ratio on galaxy colour, implying a negligible dust optical depth. There is a strong variation of spiral galaxy shapes with colour indicating the presence of dust. The intrinsic shapes of spiral galaxies in the SDSS DR6 are consistent with flat discs with a mean and dispersion of thickness to diameter ratio of (21 ± 2) per cent, and a face-on ellipticity, e, of ln(e) = -2.33 ± 0.79. Not including the effects of dust in the model leads to discs that are systematically rounder by up to 60 per cent. More luminous spiral galaxies tend to have thicker and rounder discs than lower luminosity spirals. Both elliptical and spiral galaxies tend to be rounder for larger galaxies. The marginalized value of the edge-on r-band dust extinction E 0 in spiral galaxies is E 0 ≃ 0.45 mag for galaxies of median colours, increasing to E 0 = 1 mag for g - r > 0.9 and E 0 = 1.9 for the luminous and most compact galaxies, with half-light radii <2h -1 kpc.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1eb2a1fabd71ba0f0d4a53a713fdc77893e59fcb

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Citations in the corpus

Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, result): “This distribution is consistent with that of spiral galaxies (e.g. Lambas et al. 1992; Padilla & Strauss 2008).”
Modelling the spectral energy distribution of galaxies - V. The dust and PAH emission SEDs of disk galaxies (2010, background): “…systems, but in the major part of the population of star-forming disk galaxies in the local Univers (Driver et al. 2007, Shao et al. 2007, Choi 2007, Driver et al. 2008, Unterborn & Ryden 2008, Padilla & Strauss 2008, Cho & Park 2009, Maller et al. 2009, Ganda et al. 2009, Masters et al. 2010).”
ABSORPTION-LINE PROBES OF THE PREVALENCE AND PROPERTIES OF OUTFLOWS IN PRESENT-DAY STAR-FORMING GALAXIES (2010, methodology): “We compute the galaxy inclination,i, from the measured axial ratio, b/a, and ther−band absolute magnitudeMr using Table 8 in Padilla & Strauss (2008).”
The SAMI Galaxy Survey: shocks and outflows in a normal star-forming galaxy (2014, background): “The inclination angle of SDSS J0900, as estimated from the axis ratio of 0.75 on the SDSS r-band image, is approximately 43◦ (Padilla & Strauss 2008).”
The Morphologies of Massive Galaxies at 1<z<3 in the CANDELS-UDS Field: Compact Bulges, and the Rise and Fall of Massive Disks (2012, methodology): “These histograms have been overplotted with the data points and best-fitting model from Padilla & Strauss (2008); their normalized frequencies have simply been re-scaled here by the area under our solid histogram to ease direct comparison with our results.”
GOODS-ALMA: 1.1 mm galaxy survey (2018, unknown): “Hao et al. 2006; Padilla & Strauss 2008; Li et al. 2016).”
The ATLAS3D project - II. Morphologies, kinemetric features and alignment between photometric and kinematic axes of early-type galaxies (2011, methodology): “The distribution of ellipticities of ATLAS3D galaxies is different from the distributions of ellipticities of both ‘ellipticals’ and ‘spirals’ measured in the SDSS data (Padilla & Strauss 2008).”
CALIFA : a diameter-selected sample for an integral field spectroscopy galaxy survey (2014, background): “This is a direct consequence of non-negligible extinction in the r band acting on highly inclined systems (e.g. Disney et al. 1989; Boselli & Gavazzi 1994; Unterborn & Ryden 2008; Padilla & Strauss 2008).”