Transcript Document

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
Abstract
CII at z=4.7
Recent single-dish submillimeter wavelength surveys
have revolutionized observational cosmology by
uncovering a substantial new population of dustenshrouded 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.
BR1202S
At left, we present a 3'' resolution 900 m
continuum image and a detection of the
redshifted CII line emission from the z=4.7
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 z~4.7. For
more information, see Iono et al. 2006.
BR1202N
Earliest Results
Subarcsecond Astrometry
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.
Right: APM08279+5255 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).
Most Recent Results
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
>20 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.
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.
References:
Borys, C. et al, 2006, ApJ, 636, 134
Giavalisco,M. et al, 2004, ApJ, 600, L93
Iono, D. et al, 2006, ApJ, 645, L97
Iono, D. et al, 2006, ApJ, 640, L1
Iono, D. et al, 2006b, PASJ, 58, 6 (in press)
Jannuzi, B. & Dey, A., 1999, ASP 191, p111
Pope, A. et al, 2005, MNRAS, 358, 149
Acknowledgements:
We would like to thank all the staff and postdocs at the SMA for their continued
dedication and hard work that makes these observations possible.
The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy & Astrophysics