IATE   20350
INSTITUTO DE ASTRONOMIA TEORICA Y EXPERIMENTAL
Unidad Ejecutora - UE
artículos
Título:
Angular momentum-large-scale structure alignments in LCDM models and the SDSS
Autor/es:
PAZ, DANTE J.; STASYSZYN, FEDERICO; PADILLA, NELSON D.
Revista:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Editorial:
Wiley-Blackwell
Referencias:
Lugar: Oxford; Año: 2008 vol. 389 p. 1127 - 1136
ISSN:
0035-8711
Resumen:
We study the alignments between the angular momentum of individual
objects and the large-scale structure in cosmological numerical
simulations and real data from the Sloan Digital Sky Survey, Data
Release 6 (SDSS-DR6). To this end, we measure anisotropies in the two
point cross-correlation function around simulated haloes and observed
galaxies, studying separately the one- and two-halo regimes. The
alignment of the angular momentum of dark-matter haloes in Λ cold
dark matter (ΛCDM) simulations is found to be dependent on scale
and halo mass. At large distances (two-halo regime), the spins of
high-mass haloes are preferentially oriented in the direction
perpendicular to the distribution of matter; lower mass systems show a
weaker trend that may even reverse to show an angular momentum in the
plane of the matter distribution. In the one-halo term regime, the
angular momentum is aligned in the direction perpendicular to the matter
distribution; the effect is stronger than for the one-halo term and
increases for higher mass systems.
On the observational side, we focus our study on galaxies in the
SDSS-DR6 with elongated apparent shapes, and study alignments with
respect to the major semi-axis. We study five samples of edge-on
galaxies; the full SDSS-DR6 edge-on sample, bright galaxies, faint
galaxies, red galaxies and blue galaxies (the latter two consisting
mainly of ellipticals and spirals, respectively). Using the two-halo
term of the projected correlation function, we find an excess of
structure in the direction of the major semi-axis for all samples; the
red sample shows the highest alignment (2.7 +/- 0.8per cent) and
indicates that the angular momentum of flattened spheroidals tends to be
perpendicular to the large-scale structure. These results are in
qualitative agreement with the numerical simulation results indicating
that the angular momentum of galaxies could be built up as in the Tidal
Torque scenario. The one-halo term only shows a significant alignment
for blue spirals (1.0 +/- 0.4per cent), consistent with the one-halo
results from the simulation but with a lower amplitude. This could
indicate that even though the structure traced by galaxies is adequate
to study large-scale structure alignments, this would not be the case
for the inner structure of low-mass haloes, M <=
1013h-1Msolar, an effect apparently
more important around red g - r > 0.7 galaxies.