189 research outputs found
The Power Spectrum of Galaxy Density Fluctuations: Current Results and Improved Techniques
The power spectrum of density fluctuations measured from galaxy redshift
surveys provides important constraints on models for the formation of
large-scale structure. I review current results for the 3-D power spectrum and
examine the limitations of current measurements and estimation techniques. To
span the decade of wavelength between the scales probed by galaxy surveys and
COBE, measure the detailed shape of the power spectrum, and accurately examine
the dependence of clustering on galaxy species, we require deeper samples with
carefully controlled selection criteria and improved techniques for power
spectrum estimation. I describe a new method for estimating the power spectrum
that optimally treats survey data with arbitrary geometry and sampling.Comment: 10 pages, uuencoded compressed postscript. To appear in ``Clustering
in the Universe,'' Proc. of XXXth Moriond Conference, Les Arcs, France, March
11-18, 199
The Spatial Clustering of Low Luminosity AGN
We present the first multi-parameter analysis of the narrow line AGN
clustering properties. Estimates of the two-point correlation function (CF)
based on SDSS DR2 data reveal that Seyferts are clearly less clustered than
normal galaxies, while the clustering amplitude (r_0) of LINERs is consistent
with that of the parent galaxy population. The similarities in the host
properties (color and concentration index) of Seyferts and LINERs suggest that
the difference in their r_0 is not driven by the morphology-density relation.
We find that the luminosity of [O I] emission shows the strongest influence on
AGN clustering, with low L([O I]) sources having the highest r_0. This trend is
much stronger than the previously detected dependence on L([O III]), which we
confirm. There is a strong correspondence between the clustering patterns of
objects of given spectral type and their physical properties. LINERs, which
exhibit high r_0, show the lowest luminosities and obscuration levels, and
relatively low gas densities (n_e), suggesting that these objects harbor black
holes that are relatively massive yet weakly active or inefficient in their
accretion, probably due to the insufficiency of their fuel supply. Seyferts,
which have low r_0, are luminous and show large n_e, suggesting that their
black holes are less massive but accrete quickly and efficiently enough to
clearly dominate the ionization. The low r_0 of the H II galaxies can be
understood as a consequence of both the morphology-density and star formation
rate-density relations, however, their spectral properties suggest that their
centers hide amidst large amounts of obscuring material black holes of
generally low mass whose activity remains relatively feeble. Our own Milky Way
may be a typical such case.[abridged]Comment: 27 pages, color figures, some are severely degraded in resolution,
emulateapj. See http://www.physics.drexel.edu/~constant/work/agnclustering.ps
for high resolution version. Accepted to Ap
- …