Bibcode
Leggett, Sandy; Burningham, Ben; Lodieu, Nicolas; Lucas, Phil; Marley, Mark; Pinfield, David; Saumon, Didier; Warren, Steve
Referencia bibliográfica
Spitzer Proposal ID #80077
Advertised on:
5
2011
Número de citas
0
Número de citas referidas
0
Descripción
Warm IRAC [3.6] and [4.5] photometry is critical for understanding the
cold population of brown dwarfs now being found, objects which have more
in common with planets than stars. As effective temperature drops from
800K to 400K, the fraction of flux emitted beyond 3um increases rapidly,
from about 40% to >75%. This rapid increase makes a color like
H-[4.5] a very sensitive temperature indicator, and it can be combined
with a gravity and metallicity sensitive color like H-K to constrain all
three of these fundamental properties - temperature, gravity and
metallicity - which in turn gives us mass and age for these, generally
isolated, slowly cooling objects. Our goal is to accurately characterise
the temperature/ gravity/ metallicity distribution of the coolest brown
dwarfs being found in the UKIRT Infrared Deep Sky Survey (UKIDSS) and
the Visible and Infrared Survey Telescope for Astronomy (VISTA), which
is only possible if IRAC photometry is available to complement our
near-infrared data. While data at similar wavelengths will be provided
by WISE for a sample of brown dwarfs, there are large differences
between the photometric systems, which will be dependent on metallicity,
gravity and the degree of turbulent mixing. Hence to fully exploit the
sample of cold T dwarfs found by the near- and mid-infrared sky surveys,
and to provide a homogeneous dataset for all ultracool dwarfs, a large
number of sources must be observed in both the IRAC and WISE filter
sets. Furthermore, different populations will be identified by the
different surveys, and the number of cold brown dwarfs will be small,
hence IRAC follow- up of UKIDSS, VISTA and WISE brown dwarfs is
extremely valuable. The Cycle 8 time will increase the number of
400-600K near-infrared-selected brown dwarf (a sample with mass 5-20
M_Jupiter) that have IRAC data to ~25, a significant increase of ~50%.
We expect to trigger eleven low impact ToO observations during Cycle 8,
totalling 9.9 hours of AORs.