The Panchromatic Hubble Andromeda Treasury


The Panchromatic Hubble Andromeda Treasury is a Hubble Space Telescope Multi-cycle program to map roughly a third of M31’s star forming disk, using 6 filters covering from the ultraviolet through the near infrared.  With HST’s resolution and sensitivity, the disk of M31 will be resolved into more than 100 million stars, enabling a wide range of scientific endeavors.


Primary Science Goals

  1. 23 “bricks”, each consisting of an efficient 3x6 array of HST pointings

  2. 2 orbits per pointing.

  3. Filters: F275W+F336W (WFC3/UVIS), F475W+F814W (ACS/WFC), F110W+F160W (WFC3/IR)

  4. Depth: UVIS data reach a magnitude limit of ~25 in F275W and F336W.  ACS data reach maximum depths of ~28 magnitudes in F475W and ~27 magnitudes in F814W in the uncrowded outer disk.  In these same regions, WFC3/IR data reach maximum depths of ~26.5 and ~25.5 in F110W and F160W, respectively.  However, the depth is crowding limited in the optical and NIR, and thus is a strong function of radius.  As a result, photometry in the inner bulge fields is far shallower.

Key Survey Features

  1. Star formation histories derived on ~50 parsec scales

  2. Improved stellar evolution models, calibrated at UV through NIR wavelengths

  3. Well-defined catalogs of stellar clusters, at all ages

  4. Characterization of variations in the stellar mass function from ~3 to 30 solar masses

  5. Measurements of the mass function and age distributions of stellar clusters

  6. Maps of extinction from dust, and characterization of the extinction law

  7. Calibration of star formation indicators

  8. Age dating of supernova remnants

  9. Quantitative constraints on the coupling between star formation and the interstellar medium

  10. Identification and characterization of variable stars

  11. Kinematic decompositions of structural components

  12. Cross-identification of multi-wavelength sources and emission line objects