page lim updated-1107214566Assigned ID: 444
----- Attempting Submission 1 (Fri Apr 11 12:36:30 GMT 2014) -----
HST Phase I Proposal 444 (m101-halo.apt) successfully submitted.
----- Attempting Submission 2 (Fri Apr 11 12:41:36 GMT 2014) -----
HST Phase I Proposal 444 (m101-halo.apt) successfully submitted.
----- Attempting Submission 3 (Fri Apr 11 14:05:11 GMT 2014) -----
HST Phase I Proposal 444 (m101-halo.apt) successfully submitted.
----- Attempting Submission 4 (Fri Apr 11 15:52:00 GMT 2014) -----
HST Phase I Proposal 444 (m101-halo.apt) successfully submitted.
----- Attempting Submission 5 (Fri Apr 11 18:04:20 GMT 2014) -----
HST Phase I Proposal 444 (m101-halo.apt) successfully submitted.
----- Attempting Submission 6 (Fri Apr 11 18:45:06 GMT 2014) -----
HST Phase I Proposal 444 (m101-halo.apt) successfully submitted.POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTURE
POS TARG OUTSIDE OF APERTUREfirst submission of phase 2. David R-S exposure time distribution, updated pointings
(to reflect assumed 7 Mpc distance in van Dokkum 2014)-618906929----- Attempting Submission 1 (Thu Jul 24 08:43:23 GMT 2014) -----POS TARG is outside the FOV og WFC3 and ACS on purpose.
The positioning is such that the fields span galactocentric radius from M101 in
a series of increments (33, 42, 45, 55, 60 and 72 kpc assuming 7 Mpc).The Anemic Stellar Halo of M101Models of galaxy formation in a cosmological context predict that massive disk galaxies should have richly-structured extended stellar halos, containing ~10% of a galaxy's stars, originating in large part from the tidal disruption of dwarf galaxies. Observations of a number of nearby disk galaxies have generally agreed with these expectations.
Recent new observations in integrated light with a novel array of low scattered-light telephoto lenses have failed to convincingly detect a stellar halo in the nearby massive face-on disk galaxy M101 (van Dokkum et al. 2014). They argue that any halo has to have <0.3% of the mass of the galaxy. This halo would be the least massive of any massive disk galaxy in the local Universe (by factors of several) -- such a halo is not predicted or naturally interpreted by the models, and would present a critical challenge to the picture of ubiquitous stellar halos formed from the debris of disrupting dwarf galaxies.
We propose to resolve the stellar populations of this uniquely anemic stellar halo for 6 orbits with HST (ACS and WFC3), allowing us to reach surface brightness limits sufficient to clearly detect and characterize M101's stellar halo if it carries more than 0.1% of M101's mass. With resolved stellar populations, we can use the gradient of stellar populations as a function of radius to separate stellar halo from disk, which is impossible using integrated light observations. The resolved stellar populations will reveal the halo mass to much greater accuracy, measure the halo radial profile, constrain any halo lopsidedness, estimate the halo's stellar metallicity, and permit an analysis of outer disk stellar populations.The observations are designed to probe the anemic halo of M101.
We have placed three pointings at 40, 55 and 75 kpc away from the center with
ACS parallel observations aligned with the major axis of M101.
We alternate between East-West along this axis.
We have checked to the best of our abilities against accidental overlaps with the other Cycle 22 M101 programs: 13682, 13701 and 13691
Orientation is chosen such that the ACS field is away from M101. However, the reciprocal angle would be acceptable (ACS field on the inside) if it aids with scheduling.RESOLVED STELLAR POPULATIONSDefaultfalsefalsefalsefalsefalseSUPPORTEDGALAXYDISKHALOSPIRALThis object was generated by the targetselector and retrieved from the SIMBAD database.J2000J2000GALAXYDISKHALOSPIRALJ2000J2000GALAXYDISKHALOSPIRALJ2000J2000WFC3/UVISImagingNoNoF814WWFC3/UVISImagingNoNoF606WACS/WFCImagingNoNoF814WACS/WFCImagingNoNoF606WWFC3/UVISImagingNoNoF814WWFC3/UVISImagingNoNoF606WACS/WFCImagingNoNoF814WACS/WFCImagingNoNoF606WWFC3/UVISImagingNoNoF814WWFC3/UVISImagingNoNoF606WACS/WFCImagingNoNoF814WACS/WFCImagingNoNoF606WThe scheduling data was generated by CASM 22.2.CASM was run in Phase II mode./private/var/folders/j1/wxrbrp5s5wjcpv146ln6lbs00005wj/T/OPVisit676636098961844375.xml(Tic-Visit
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