38 research outputs found
Remote Observing with the Keck Telescope Using the ACTS Satellite
As a technical demonstration project for the NASA Advanced Communications Technology Satellite (ACTS), we have implemented remote observing on the 10-meter Keck II telescope on Mauna Kea in Hawaii from the California Institute of Technology campus in Pasadena. The data connection consists of optical fiber networks in Hawaii and California, connecting the end-points to high data rate (HDR) ACTS satellite antennae at JPL in Pasadena and at the Tripler Army Medical Center in Honolulu. The terrestrial fiber networks run the asynchronous transfer mode (ATM) protocol at DS-3 (45 Mbit/sec) speeds, providing ample bandwidth to enable remote observing with a software environment identical to that used for on-site observing in Hawaii. This experiment has explored the data requirements of remote observing with a modern research telescope and large-format detector arrays. While the maximum burst data rates are lower than those required for many other applications (e.g., HDTV), the network reliability and data integrity requirements are critical. As we show in this report, the former issue particularly may be the greatest challenge for satellite networks for this class of application. We have also experimented with the portability of standard TCP/IP applications to satellite networks, demonstrating the need for alternative TCP congestion algorithms and minimization of bit error rates (BER). Reliability issues aside, we have demonstrated that true remote observing over high-speed networks provides several important advantages over standard observing paradigms. Technical advantages of the high-speed network access include more rapid download of data to a user's home institution and the opportunity for alternative communication facilities between members of an observing team, such as audio- and videoconferencing
The Extremely Red Objects Found Thus Far in the Caltech Faint Galaxy Redshift Survey
We discuss the very red objects found in the first field of the Caltech Faint
Galaxy Redshift Survey, for which the observations and analysis are now
complete. In this field, which is 15 arcmin and at J005325+1234 there are
195 objects with mag, of which 84% have redshifts. The sample
includes 24 spectroscopically confirmed Galactic stars, 136 galaxies, three
AGNs, and 32 objects without redshifts.
About 10% of the sample has mag. Four of these objects have
redshifts, with . Three of these are based on absorption
features in the mid-UV, while the lowest redshift object shows the standard
features near 4000\AA. Many of the objects still without redshifts have been
observed spectroscopically, and no emission lines were seen in their spectra.
We believe they are galaxies with that are red due to their
age and stellar content and not to some large amount of internal reddening from
dust.
Among the many other results from this survey of interest here is a
determination of the median extinction in the mid-UV for objects with strong
emission line spectra at . The result is extinction by a factor
of 2 at 2400\AA.Comment: 6 pages, Latex, with 2 figures. To be published in the proceedings of
the conference "Infrared Surveys: A Prelude to SIRTF
Caltech Faint Galaxy Redshift Survey VII: Data Analysis Techniques and Redshifts in the Field J0053+1234
We present the techniques used to determine redshifts and to characterize the
spectra of objects in the Caltech Faint Galaxy Redshift Survey in terms of
spectral classes and redshift quality classes. These are then applied to
spectra from an investigation of a complete sample of objects with mag
in a 2 by 7.3 arcmin^2 field at J005325+1234. Redshifts were successfully
obtained for 163 of the 195 objects in the sample; these redshifts lie in the
range [0.173, 1.44] and have a median of 0.58 (excluding 24 Galactic stars).
The sample includes two broad lined AGNs and one QSO.Comment: 20 pages, Latex, 3 figures, accepted for publication in the ApJ
Supplement
Caltech Faint Galaxy Redshift Survey. VIII. Analysis of the Field J0053+1234
The results of a spectroscopic investigation of a complete sample of objects with K_s1.5, and the galaxies in such groups appear to be coeval and to show little sign of ongoing star formation. The galaxies outside the redshift peaks are also clustered, albeit more weakly, are less luminous and more frequently exhibit strong emission lines. These "isolated" galaxies therefore appear, on average, to form stars at later epochs than the strongly clustered galaxies. The galaxy spectral energy distributions (SEDs) derived from our UBVRIK photometry are also very closely correlated with the galaxy spectral types and luminosities. These results have strong implications for the analysis of redshift surveys at intermediate redshift. The sample is used to investigate the evolution of the combined galaxy luminosity function back to z=0.8. No significant change is found in the characteristic luminosity L*, and only weak color changes are detected, consistent with passive evolution. The blue galaxy-luminosity function is more dwarf rich than the red galaxy-luminosity function. No significant change in the comoving density is found in this sample out to z~1.4, assuming that the objects without redshifts (16% of the sample) are galaxies, essentially all of which have z>0.8. This suggests that mergers are not important among the objects in this sample. A population of extremely red objects with (R-K)>5 mag exists in the infrared-selected sample; all four such objects with redshifts are found to be absorption-line galaxies with z~1. Most of the very red objects therefore appear to be galaxies with z≳1 that are not heavily reddened by dust. A measure of the UV extinction at 2400 Å for the emission-line galaxies of a factor of 2 is obtained, implying only modest UV extinction in high-redshift star-forming galaxies
Redshift clustering in the Hubble Deep Field
We present initial results from a redshift survey carried out with the Low
Resolution Imaging Spectrograph on the 10~m W. M. Keck Telescope in the Hubble
Deep Field. In the redshift distribution of the 140 extragalactic objects in
this sample we find 6 strong peaks, with velocity dispersions of
{\kms}. The areal density of objects within a particular peak, while
it may be non-uniform, does not show evidence for strong central concentration.
These peaks have characteristics (velocity dispersions, density enhancements,
spacing, and spatial extent) similar to those seen in a comparable redshift
survey in a different high galactic latitude field (Cohen et al 1996),
confirming that the structures are generic. They are probably the high redshift
counterparts of huge galaxy structures (``walls'') observed locally.Comment: 14 pages, including 2 figures, to appear in ApJ Letter
Caltech Faint Galaxy Redshift Survey X: A Redshift Survey in the Region of the Hubble Deep Field North
A redshift survey has been carried out in the region of the Hubble Deep Field
North using the Low Resolution Imaging Spectrograph at the Keck Observatory.
The resulting redshift catalog, which contains 671 entries, is a compendium of
our own data together with published LRIS/Keck data. It is more than 92%
complete for objects, irrespective of morphology, to mag in the HDF
itself and to mag in the Flanking Fields within a diameter of 8 arcmin
centered on the HDF, an unusually high completion for a magnitude limited
survey performed with a large telescope. A median redshift is reached
at .
Strong peaks in the redshift distribution, which arise when a group or poor
cluster of galaxies intersect the area surveyed, can be identified to in this dataset. More than 68% of the galaxies are members of these
redshift peaks. In a few cases, closely spaced peaks in can be resolved
into separate groups of galaxies that can be distinguished in both velocity and
location on the sky.
The radial separation of these peaks in the pencil-beam survey is consistent
with a characteristic length scale for the their separation of 70 Mpc
in our adopted cosmology (, ). Strong
galaxy clustering is in evidence at all epochs back to . (abstract
abridged)Comment: Accepted to the ApJ. This version contains all the figures and
tables. 2 minor typos in table 2b correcte
Caltech Faint Galaxy Redshift Survey. VIII. Analysis of the Field J0053+1234
The results of a spectroscopic investigation of a complete sample of objects with K_s1.5, and the galaxies in such groups appear to be coeval and to show little sign of ongoing star formation. The galaxies outside the redshift peaks are also clustered, albeit more weakly, are less luminous and more frequently exhibit strong emission lines. These "isolated" galaxies therefore appear, on average, to form stars at later epochs than the strongly clustered galaxies. The galaxy spectral energy distributions (SEDs) derived from our UBVRIK photometry are also very closely correlated with the galaxy spectral types and luminosities. These results have strong implications for the analysis of redshift surveys at intermediate redshift. The sample is used to investigate the evolution of the combined galaxy luminosity function back to z=0.8. No significant change is found in the characteristic luminosity L*, and only weak color changes are detected, consistent with passive evolution. The blue galaxy-luminosity function is more dwarf rich than the red galaxy-luminosity function. No significant change in the comoving density is found in this sample out to z~1.4, assuming that the objects without redshifts (16% of the sample) are galaxies, essentially all of which have z>0.8. This suggests that mergers are not important among the objects in this sample. A population of extremely red objects with (R-K)>5 mag exists in the infrared-selected sample; all four such objects with redshifts are found to be absorption-line galaxies with z~1. Most of the very red objects therefore appear to be galaxies with z≳1 that are not heavily reddened by dust. A measure of the UV extinction at 2400 Å for the emission-line galaxies of a factor of 2 is obtained, implying only modest UV extinction in high-redshift star-forming galaxies