Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deep HST Imaging of Sextans A I. The Spatially Resolved Recent Star
  Formation History   We have measured stellar photometry from deep Cycle 7 Hubble Space
Telescope/WFPC2 imaging of the dwarf irregular galaxy Sextans A. The imaging
was taken in three filters: F555W ($V$; 8 orbits), F814W ($I$; 16 orbits), and
F656N (H$\alpha$; 1 orbit). Combining these data with Cycle 5 WFPC2
observations provides nearly complete coverage of the optically visible portion
of the galaxy. The Cycle 7 observations are nearly 2 magnitudes more sensitive
than the Cycle 5 observations, which provides unambiguous separation of the
faint blue helium burning stars (BHeB stars) from contaminant populations. The
depth of the photometry allows us to compare recent star formation histories
recovered from both the main sequence (MS) stars and the BHeB stars for the
last 300 Myr. The excellent agreement between these independent star formation
rate (SFR) calculations is a resounding confirmation for the legitimacy of
using the BHeB stars to calculate the recent SFR. Using the BHeB stars we have
calculated the global star formation history over the past 700 Myr. The history
calculated from the Cycle 7 data is remarkably identical to that calculated
from the Cycle 5 data, implying that both halves of the galaxy formed stars in
concert. We have also calculated the spatially resolved star formation history,
combining the fields from the Cycle 5 and Cycle 7 data. Our interpretation of
the pattern of star formation is that it is an orderly stochastic process.

10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn