Detalles de publicación
PP 09032
The Origin of the Light Distribution in Spiral Galaxies
(1) Instituto de Astrofisica de Canarias, c/Via Lactea s/n, E38205, La Laguna, Tenerife, Spain
(2) 1Jeremiah Horrocks Institute for Astrophysics and Supercomputing,Preston, PR1 2HE, UK
We analyse a high-resolution, fully cosmological, hydrodynamical disc galaxy simulation,
to study the source of the double-exponential light profiles seen in many stellar
discs, and the effects of stellar radial migration upon the spatio-temporal evolution of
both the disc age and metallicity distributions. We find a “break” in the pure exponential
stellar surface brightness profile, and trace its origin to a sharp decrease in the
star formation per unit surface area, itself produced by a decrease in the gas volume
density due to a warping of the gas disc. Star formation in the disc continues well
beyond the break. We find that the break is more pronounced in bluer wavebands. By
contrast, we find little or no break in the mass density profile. This is, in part, due to
the net radial migration of stars towards the external parts of the disc. Beyond the
break radius, we find that 60% of the resident stars migrated from the inner disc,
while 25% formed in situ. Our simulated galaxy also has a minimum in the age profile
at the break radius but, in disagreement with some previous studies, migration is
not the main mechanism producing this shape. In our simulation, the disc metallicity
gradient flattens with time, consistent with an “inside-out” formation scenario. We do
not find any difference in the intensity or the position of the break with inclination,
suggesting that perhaps the differences found in empirical studies are driven by dust
extinction.
to study the source of the double-exponential light profiles seen in many stellar
discs, and the effects of stellar radial migration upon the spatio-temporal evolution of
both the disc age and metallicity distributions. We find a “break” in the pure exponential
stellar surface brightness profile, and trace its origin to a sharp decrease in the
star formation per unit surface area, itself produced by a decrease in the gas volume
density due to a warping of the gas disc. Star formation in the disc continues well
beyond the break. We find that the break is more pronounced in bluer wavebands. By
contrast, we find little or no break in the mass density profile. This is, in part, due to
the net radial migration of stars towards the external parts of the disc. Beyond the
break radius, we find that 60% of the resident stars migrated from the inner disc,
while 25% formed in situ. Our simulated galaxy also has a minimum in the age profile
at the break radius but, in disagreement with some previous studies, migration is
not the main mechanism producing this shape. In our simulation, the disc metallicity
gradient flattens with time, consistent with an “inside-out” formation scenario. We do
not find any difference in the intensity or the position of the break with inclination,
suggesting that perhaps the differences found in empirical studies are driven by dust
extinction.