PAndromeda - A Dedicated Deep Survey of M31 with Pan-STARRS 1
Abstract
PAndromeda monitors M31 for 2% of the overall PS1 time. This corresponds to 0.5 h per night during a period of 5 months per year. PAndromeda is designed to identify gravitational microlensing events, caused by bulge and disk stars (self-lensing) and by compact matter in the halos of M31 and the MW (halo lensing, or lensing by MACHOs). The main science goals of PAndromeda are measuring the masses and mass-fraction of compact objects in the M31 and MW halos, and constraining the M31 bulge mass function at the low mass end. As a side product PAndromeda is also able to search for microlensing events towards M32 and NGC205. The interpretation of the microlensing events requires understanding the mix of stellar ages and metalicities in the bulge, disk, and halo of M31 as obtained from resolved stellar populations (census of supergiants, OB-associations, analysis of CMD diagrams as a function of location), variability studies (Cepheids to LPVs), and color gradients in the light profiles. All these informations can directly extracted from the PAndromeda data itself. During the first season 2010 PAndromeda monitored M31 from end of July 2010 till end of December 2010 on 91 nights (58%). In total 1782 images were exposed, on 90 nights in r' and on 66 in i' band. The total amount of reduced data is 14 TB. From the 2010 season we analyzed the central field of M31 (21'x21'). This is to test the detection process in the field where we expect the highest lensing rate because of self lensing. So far we detected 3 high quality microlensing light-curves. The third one is very bright with 19 mag in r'. Such high flux excess events are more difficult to reconcile with self-lensing than with halo-lensing. The full data set is currently analyzed.
- Publication:
-
American Astronomical Society Meeting Abstracts #218
- Pub Date:
- May 2011
- Bibcode:
- 2011AAS...21811315R