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Session 81 - Dwarf Galaxies.
Display session, Friday, January 09
Exhibit Hall,

[81.03] A Possible Detection of the Sgr dSph at b=-40 deg

M. H. Siegel, S. R. Majewski (U. Virginia), I. N. Reid (Caltech), I. Thompson (OCIW), A. U. Landolt (LSU), W. E. Kunkel (OCIW)

As part of the Selected Areas Starcount Survey (SASSY), a CCD survey to V=21, we have obtained VI photometry of two fields placed along the major axis of the Sagittarius (Sgr) dwarf spheroidal galaxy at b=\pm 40^\circ. Comparison of the field star color-magnitude diagram (CMD) for these fields to the CMDs of fields reflected about the Galactic l=0^\circ meridian reveals an excess of stars at V=18.1 and 0.98 < V-I < 1.18 -- consistent with expectations for a Sgr red giant clump -- in the l=11^\circ, b=-40^\circ field. The excess appears to be confined to three adjacent 0.13 deg^2 subfields in this direction of the sky. No similar excess appears in our field at l=353^\circ, b=+41^\circ or in two other comparison fields. Deeper CCD imaging at the position of the possible Sgr red giant clump stars reveals an apparent main sequence turn off at 21 < V < 24, also consistent with the presence of the Sgr tidal extension at this Galactic latitude. This detection more than doubles the known extent of the Sgr tidal stream. Our apparent non-detection of Sgr at at b=+40 may indicate a maximum age to the stream of 1500 Myr, but may also be attributable to our northern survey field not being placed precisely along the orbit of Sgr, or a substantially reduced sky density at this large distance from its center.

Program listing for Friday