The Millennium Galaxy Catalogue: The severe attenuation of bulge flux by dusty spiral discs

Abstract

Using the Millennium Galaxy Catalogue we quantify the dependency of the disc and bulge luminosity functions on galaxy inclination. Using a contemporary dust model we show that our results are consistent with galaxy discs being optically thick in their central regions (tau_B^f=3.8+/-0.7). As a consequence the measured B-band fluxes of bulges can be severely attenuated by 50% to 95% depending on disc inclination. We argue that a galaxy's optical appearance can be radically transformed by simply removing the dust, e.g. during cluster infall, with mid-type galaxies becoming earlier, redder, and more luminous. Finally we derive the mean photon escape fraction from the integrated galaxy population over the 0.1micron to 2.1 micron range, and use this to show that the energy of starlight absorbed by dust (in our model) is in close agreement with the total far-IR emission.

arXiv commentContributed article to IAU Symp. 245 on "The Formation and Evolution of Galaxy Bulges", (eds M. Bureau, E. Anthanassoula & B. Barbury)

References in corpus (6)

• The Millennium Galaxy Catalogue: Bulge/Disc Decomposition of 10095 Nearby Galaxies
• The Millennium Galaxy Catalogue: the B-band attenuation of bulge and disc light and the implied cosmic dust and stellar mass densities
• The Millennium Galaxy Catalogue: 16 < B_MGC < 24 galaxy counts and the calibration of the local galaxy luminosity function
• The Millennium Galaxy Catalogue: the space density and surface brightness distribution(s) of galaxies
• Dust Attenuation in Late-Type Galaxies. I. Effects on Bulge and Disk Components
• The Opacity of Nearby Galaxies from Colors and Counts of Background Galaxies: I. The Synthetic Field Method and its Application to NGC 4536 and NGC 3664