- ID:
- ivo://CDS.VizieR/J/AJ/119/486
- Title:
- HDF-S: STIS imaging
- Short Name:
- J/AJ/119/486
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the imaging observations made with the Space Telescope Imaging Spectrograph (STIS) of the Hubble Deep Field South. The field was imaged in four bandpasses: a clear CCD bandpass for 156ks, a long-pass filter for 22-25ks/pix typical exposure, a near-UV bandpass for 23ks, and a far-UV bandpass for 52ks. The clear, visible image is the deepest observation ever made in the UV-optical wavelength region, reaching a 10{sigma}AB magnitude of 29.4 for an object of area 0.2arcsec^2^. The field contains QSO J2233-606, the target of the STIS spectroscopy, and extends 50"x50" for the visible images, and 25"x25" for the ultraviolet images. We present the images, catalog of objects, and galaxy counts obtained in the field.
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- ID:
- ivo://CDS.VizieR/J/AJ/116/146
- Title:
- UGC 6456 HST photometry
- Short Name:
- J/AJ/116/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry on the UVI system has been performed on the resolved stellar content of the blue compact dwarf galaxy UGC 6456 using Wide Field Planetary Camera 2 (WFPC2) images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram (CMD) goes to about V=27.5 and reveals not only a young population of blue main-sequence stars and blue and red supergiants, but also an older evolved population of red giants and a fairly well represented asymptotic giant branch. The distance to the galaxy is estimated from the tip of the red giant branch to be 4.5Mpc, placing it about 1.5Mpc farther away than the major members of the M81 Group, with which it is usually associated. The youngest stars are generally associated with H ii regions shown on our Halpha image and are largely confined to the 745pc field of our PC images. A comparison of their distribution in the CMD with theoretical isochrones suggests ages from 4 to 10Myr. The population of older stars is found throughout all WFPC2 camera fields and seems to show an elliptical distribution with an aspect ratio of about 2.4 and an exponential falloff in surface density with distance from a center of symmetry that is not far from the centroid of the youngest stars. Theoretical modeling of the CMD at a metallicity of Z=0.001 suggests star formation in the age interval 1-2Gyr, a strong burst in the interval 600-800Myr, and a lower rate of star formation up to the present. The evidence is compatible with a scenario beginning with the formation of a population of low-metallicity stars, enriching a major residual of prestellar material that subsequently fueled an active episode of star formation. That burst of star formation must have been particularly spectacular and may be related to the activity we now see in the distant blue dwarf galaxies revealed in deep imaging.
