The Faint Object Camera (FOC) was one of the 4 original axial instruments on the Hubble Space Telescope (HST). FOC is used to make high-resolution observations of faint sources at UV and visible wavel

The High Speed Photometer (HSP) was one of the four original axial instruments on the Hubble Space Telescope (HST). The HSP was designed to make very rapid photometric observations of astrophysical sources in a variety of filters and passbands from the near ultraviolet to the visible. The HSP was removed from HST during the First Servicing Mission in December, 1993.

The Space Telescope Imaging Spectrograph (STIS) was installed in HST on Feb. 14, 1997, replacing the GHRS spectrograph. STIS provides spectra and images at ultraviolet and visible wavelengths, probing the Universe from our solar system out to cosmological distances.

The Faint Source Survey (FSS) is the definitive IRAS data set for faint point sources. The FSS was produced by point-source filtering the individual detector data streams and then coadding those data streams using a trimmed-average algorithm. The resulting images, or plates, give the best estimate from the IRAS survey data of the point source flux density at every surveyed point of the sky. The Faint Source Catalog (FSC) is a compilation of the sources extracted from the FSS plates that have met reasonable reliability requirements. Averaged over the whole catalog, the FSC is at least 98.5% reliable at 12 and 25 microns, and ~94% at 60 microns. For comparison, the IRAS Point Source Catalog (PSC) is > 99.997% reliable, but the sensitivity of the FSC exceeds that of the PSC by about a factor of 2.5. The FSC contains data for 173,044 point sources in unconfused regions with flux densities typically greater than 0.2 Jy at 12, 25, and 60 microns and greater than 1.0 Jy at 100 microns.

Hubble Space Telescope (HST) is an orbiting astronomical observatory operating from the near-infrared into the ultraviolet. Launched in 1990 and scheduled to operate through 2010, HST carries and has carried a wide variety of instruments producing imaging, spectrographic, astrometric, and photometric data through both pointed and parallel observing programs. MAST is the primary archive and distribution center for HST data, distributing science, calibration, and engineering data to HST users and the astronomical community at large. Over 100 000 observations of more than 20 000 targets are available for retrieval from the Archive.

Dwarf spheroidal (dSph) galaxies are key objects in near-field cosmology, especially in connection to the study of galaxy formation and evolution at small scales. In addition, dSphs are optimal targets to investigate the nature of dark matter. However, while we begin to have deep optical photometric observations of the stellar population in these objects, little is known so far about their diffuse emission at any observing frequency, and hence on thermal and non-thermal plasma possibly residing within dSphs. In this paper, the authors present deep radio observations of six local dSphs performed with the Australia Telescope Compact Array (ATCA) at 16 cm wavelength (2100 MHz frequency). They mosaicked a region of radius of about 1 degree around three 'classical' dSphs (CDS), Carina, Fornax, and Sculptor, and of about half of degree around three 'ultrafaint' dSphs (UDS), Bootes II, Segue 2, and Hercules. The rms noise level is below 0.05 mJy for all the maps. The restoring beams full width at half-maximum (FWHM) ranged from (4.2 arcseconds by 2.5 arcseconds) to (30.0 arcseconds by 2.1 arcseconds) in the most elongated case. A catalog, including the 1392 sources detected in the six dSph fields, is presented here. In the reference paper, the main properties of the background sources are discussed, with the positions and fluxes of the brightest objects compared with the FIRST, NVSS, and SUMSS observations of the same fields. The observed population of radio emitters in these fields is dominated by synchrotron sources.The authors have computed the associated source number counts at 2 GHz down to fluxes of 0.25 mJy, which prove to be in agreement with AGN count models. The observations presented in this paper were performed during 2011 July. The project was allocated a total of 123 h of ATCA observing time. The spectral setup included the simultaneous observation of a 2-GHz-wide band centered at 2100 MHz with a 1 MHz spectral resolution for continuum observations (recording all four polarization signals). The mapping of the three CDS required a 19 field-mosaic with a total on-source integration time of about 1 hour per field. For Bootes II and Hercules, a 7 field-mosaic with an on-source integration time of about 2 hours per field was chosen, while Segue 2, due to its smaller size,was imaged with a 3 field-mosaic with about 4 hours per field of integration time (with the purpose of maximizing the sensitivity). More precisely, a total of 16.5, 15.0, 17.0, 13.0, 10.9, and 9.6 hours were spent on-source for Carina, Fornax, Sculptor, Bootes II, Hercules, and Segue 2, respectively. The nominal rms sensitivity in each panel for the actual observing time was 36, 38, 35, 25, 28, and 20 µJy for Carina, Fornax, Sculptor, Bootes II, Hercules, and Segue 2, respectively. See Table 1 of the reference paper for the details of the average restoring beam parameters across all mosaic panels for each field of view (FoV). The authors used two automated routines for source extraction and cataloging, which are provided by the SEXTRACTOR package (Bertin & Arnouts 1996, A&AS, 117, 393) and the task SFIND in MIRIAD. In these maps, SFIND and SEXTRACTOR give nearly identical results for astrometry (number of sources and positions), once the threshold parameters in SEXTRACTOR are tuned (the authors found a threshold typically slightly above 5 sigma). The mismatch in positions is random, and about 1 arcsecond on average for all FoVs. This value can be taken as an estimate of the positional accuracy. Photometry on the other hand, gave quite different results for some sources: in the catalog, the authors used the results from SFIND since this was specifically written to analyze radio images, accounting for artifacts and sidelobes. The number of sources in each dSph FoV is reported in Table 2 of the reference paper. Radio sources can be made up of different components. To decide whether nearby sources are separated sources or components of a single source, the