Using the Near-IR Galaxy Luminosity Function to test for a Large Local Void (Ryan Keenan, CTIO-La Serena)
Recent cosmological modeling efforts have shown that a local underdensity on scales of a few hundred Mpc (out to z~0.1), could produce the apparent acceleration of the expansion of the universe observed via type Ia supernovae. Several studies of galaxy counts in the near-infrared (NIR) have found that the local universe appears under-dense by 25−50% compared with regions a few hundred Mpc distant. If the local universe is under-dense in this way then the normalization of the near-infrared (NIR) galaxy luminosity function (LF) at z > 0.1 should be a factor of 1.5−2 higher than that measured for z < 0.1. Here we present a highly complete (> 90%) spectroscopic sample of 1436 galaxies selected in the H−band (1.6μm) to study the normalization of the NIR LF at 0.1 < z < 0.3 and address the question of whether or not we reside in a large local underdensity. Our survey sample consists of all galaxies brighter than 18th magnitude in the H−band drawn from six widely separated fields at high Galactic latitudes, which cover a total of 2 square degrees on the sky. We find that for the combination of our six fields, the normalization at 0.1 < z < 0.3 is roughly a factor of 1.5 higher than that measured at lower redshifts. While our statistical errors in this measurement are on the 10% level, we find the systematics due to cosmic variance are at the 15% level. We examine the effects of cosmic variance on studies of the NIR LF over the past decade and find that observations cannot yet rule out the possibility that the local universe is under-dense at z < 0.1.
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| Cuándo |
18/01/2012 de 01:00 pm a 02:00 pm |
| Dónde | DAA-PUC, Seminar Room |
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