High Angular Resolution SMA Imaging of High Redshift Galaxies at 345 GHz

1
High Angular Resolution SMA Imaging of High
Redshift Galaxies at 345 GHz
Alison Peck (CfA), Daisuke Iono (NAOJ), Glen
Petitpas (CfA) and the SMA Team
CII at z4.7
At left, we present a 3'' resolution 900 ?m
continuum image and a detection of the redshifted
CII line emission from the z4.7 QSO BR 1202-0725
obtained using the SMA. The continuum image was
made using line free channels in the lower
sideband. The angular resolution in the
continuum image is 3.4 x 2.7 and the RMS noise
is 3 mJy. The insets above show the line profile
toward the northern (BR1202N) and southern
(BR1202S) components obtained at the peak pixels.
The velocity resolution shown is 120 km s-1.
The systemic velocity marked 0 km s -1
corresponds to 334 GHz. This is one of the first
detections of the CII line from a high redshift
source. The line is associated with the northern
component, BR1202N. The low CII-FIR ratio of
3.8 x 10-4 is similar to local ULIRGs. We have
also found that X-ray emission is clearly
detected from BR1202S, and at 99.6 confidence
from BR1202N, suggesting that BR1202-0725 is the
first example of a pair of AGN hosts at z4.7.
For more information, see Iono et al. 2006.

Abstract
Recent single-dish submillimeter wavelength
surveys have revolutionized observational
cosmology by uncovering a substantial new
population of dust-enshrouded starburst galaxies
at high redshift. A tremendous amount can be
learned about the star formation history of the
universe by comparing the characteristics of
these early sources at a range of wavelengths,
from radio to x-ray. Unfortunately, the
positions of these sources are not well enough
determined in the parent surveys to justify
devoting large amounts of time using higher
resolution instruments without first performing
high precision astrometry. The Submillimeter
Array on Mauna Kea is now the ideal instrument
for this, as it can observe at the same frequency
as the original survey, but with substantially
better angular resolution, yielding astrometric
accuracies of 100 mas. We present images of the
distant galaxies detected to date using the
Submillimeter Array at 345 GHz.
Earliest Results
Subarcsecond Astrometry
Right APM082795255 is a well known lensed
quasar with an 850 micron flux of 50 mJy
measured using SCUBA. This source was used as an
initial feasibility target in 2003 before the
detection of weaker high redshift sources was
attempted. Though we only had 5 antennas and 600
MHz bandwidth at the time, the source was
detected in 5 hours at nearly 5 sigma. The beam
shown in the lower left corner of the image is
2x2.5 arcseconds. We plan to observe this source
in the next few weeks in our Very Extended
configuration to obtain sub-arcsecond resolution,
which we hope will allow us to resolve the source
and thus put constraints on the size of the
lensed image(s).
Below The first panel shows the synthesized
image of GN 20 made by adding 2 nights of SMA
data (with astrometric verification source shown
in the inset). The contours are 1,2,3... x RMS
noise level of 2 mJy. The derived flux from a
u,v fit is 23 /- 3 mJy with a positional
uncertainty of 0.15". The central panel shows
the SMA contours overlaid on the deep Spitzer
IRAC image. The third panel shows a smaller
field with the SMA continuum contours on the HST
ACS V-band image. Both images were obtained from
the GOODS archive (Giavalisco et al 2004). GN20
was discovered in the recent SCUBA observations
of the GOODS North Field with S/N close to 10
(Pope et al 2005). It is not detected in 450µm,
radio, or in X-ray, but its robust SCUBA
detection and a detection at 1.3 mm makes this
one of the brightest sub-mm sources discovered to
date.
Most Recent Results
Left SXDF 850.6 is a source in the SCUBA Half
Degree Extragalactic Survey (SHADES) which has
multiple possible VLA radio and Subaru optical
counterparts, but no established sub-mm source
identification. The strongest radio emission has
no confirmed optical counterpart, but the two
secondary radio peaks both have apparent optical
associations. These preliminary plots shows our
most recent result. The source detected is
consistent with the position of one of the
marginal VLA detections. The peak flux in the top
image is 6 mJy, making it the faintest high
redshift source detected at the SMA thus far. The
contours are 2,3,4 x RMS noise level of 1.4 mJy.
Above MIPS-J1428 was discovered to be the
strongest source in the Spitzer MIPS images of
the Bootes GTO field, with a flux of 240 mJy.
This source has been observed spectroscopically
at Keck, yielding a redshift z 1.5.
Subsequent SCUBA observations measured the flux
of MIPS-J1428 to be gt20 mJy at 850 µm. There is
another galaxy 2.4'' away from the MIPS
detection, but the low resolution radio map did
not allow precise identification of the sub-mm
emitting galaxy, despite its strong radio
emission. More information about this source can
be found in Iono et al. (2006) and Borys et al.
(2006), and Iono et al. (2006b) also present
recent CO(3-2) and CO(2-1) detections toward this
source. The first panel shows the synthesized
image of MIPS-J1428 made using 2 nights of SMA
observing time (with astrometric verification
source shown in the inset). The contours are
1,2,3 x RMS noise level of 2 mJy. The derived
flux from a u,v fit is 18 /- 3 mJy with a
positional uncertainty of 0.1-0.2". The second
and third panels show the SMA contours overlaid
on the NDWFS (Jannuzi Dey 1999) K- and I-band
images, respectively.
The Submillimeter Array is a joint project
between the Smithsonian Astrophysical Observatory
and the Academia Sinica Institute of Astronomy
Astrophysics