17 research outputs found
The Chemodynamics of the Stellar Populations in M31 from APOGEE Integrated Light Spectroscopy
We present analysis of nearly 1,000 near-infrared, integrated light spectra
from APOGEE in the inner 7 kpc of M31. We utilize full spectrum fitting
with A-LIST simple stellar population spectral templates that represent a
population of stars with the same age, [M/H], and [/M]. With this, we
determine the mean kinematics, metallicities, abundances, and ages of
the stellar populations of M31's bar, bulge, and inner disk (4-7 kpc). We
find a non-axisymmetric velocity field in M31 resulting from the presence of a
bar. The bulge of M31 is metal-poor relative to the disk ([M/H] =
dex), features minima in metallicity on either side
of the bar ([M/H] -0.2), and is enhanced in abundance
([/M] = ). The disk of M31 within 7 kpc
is enhanced in both metallicity ([M/H] = ) and
abundance ([/M] = ). Both of these
structural components are uniformly old at 12 Gyr. We find the
metallicity increases with distance from the center of M31, with the steepest
gradient along the disk major axis ( dex/kpc). This gradient is
the result of changing light contributions from the metal-poor bulge and
metal-rich disk. The chemodynamics of stellar populations encodes information
about a galaxy's chemical enrichment, star formation history, and merger
history, allowing us to discuss new constraints on M31's formation. Our results
provide a stepping stone between our understanding of the Milky Way and other
external galaxies
Catalog of Integrated-light Star Cluster Light Curves in TESS
We present the first integrated-light, TESS-based light curves for star clusters in the Milky Way, Small Magellanic Cloud, and Large Magellanic Cloud. We explore the information encoded in these light curves, with particular emphasis on variability. We describe our publicly available package elk , which is designed to extract the light curves by applying principal component analysis to perform background light correction and incorporating corrections for TESS systematics, allowing us to detect variability on timescales shorter than ∼10 days. We perform a series of checks to ensure the quality of our light curves, removing observations where systematics are identified as dominant features, and deliver light curves for 348 previously cataloged open and globular clusters. Where TESS has observed a cluster in more than one observing sector, we provide separate light curves for each sector (for a total of 2204 light curves). We explore in detail the light curves of star clusters known to contain high-amplitude Cepheid and RR Lyrae variable stars, and we confirm that the variability of these known variables is still detectable when summed together with the light from thousands of other stars. We also demonstrate that even some low-amplitude stellar variability is preserved when integrating over a stellar population
Clusters, Clouds, and Correlations: Relating Young Clusters to Giant Molecular Clouds in M33 and M31
We use young clusters and giant molecular clouds (GMCs) in the galaxies M33
and M31 to constrain temporal and spatial scales in the star formation process.
In M33, we compare the PHATTER catalogue of 1214 clusters with ages measured
via colour-magnitude diagram (CMD) fitting to 444 GMCs identified from a new 35
pc resolution ALMA CO(2-1) survey. In M31, we compare the PHAT catalogue
of 1249 clusters to 251 GMCs measured from a CARMA CO(1-0) survey with
20 pc resolution. Through two-point correlation analysis, we find that young
clusters have a high probability of being near other young clusters, but
correlation between GMCs is suppressed by the cloud identification algorithm.
By comparing the positions, we find that younger clusters are closer to GMCs
than older clusters. Through cross-correlation analysis of the M33 cluster
data, we find that clusters are statistically associated when they are 10
Myr old. Utilizing the high precision ages of the clusters, we find that
clusters older than Myr are uncorrelated with the molecular ISM.
Using the spatial coincidence of the youngest clusters and GMCs in M33, we
estimate that clusters spend 4-6 Myr inside their parent GMC. Through
similar analysis, we find that the GMCs in M33 have a total lifetime of
-15 Myr. We also develop a drift model and show that the above
correlations can be explained if the clusters in M33 have a 5-10 km s
velocity dispersion relative to the molecular ISM.Comment: 14 pages, 13 figures, 1 tables, accepted for publication at MNRA