5 research outputs found
Resolved SPLASH Chemodynamics in Andromeda's PHAT Stellar Halo and Disk: On the Nature of the Inner Halo Along the Major Axis
Stellar kinematics and metallicity are key to exploring formation scenarios
for galactic disks and halos. In this work, we characterized the relationship
between kinematics and photometric metallicity along the line-of-sight to M31's
disk. We combined optical HST/ACS photometry from the Panchromatic Hubble
Andromeda Treasury (PHAT) survey with Keck/DEIMOS spectra from the
Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo (SPLASH)
survey. The resulting sample of 3536 individual red giant branch stars spans
4-19 projected kpc, making it a useful probe of both the disk and inner halo.
We separated these stars into disk and halo populations by modeling the
line-of-sight velocity distributions as a function of position across the disk
region, where 70.9% stars have a high likelihood of belonging to the disk and
17.1% to the halo. Although stellar halos are typically thought to be
metal-poor, the kinematically identified halo contains a significant population
of stars (29.4%) with disk-like metallicity ([Fe/H]).
This metal-rich halo population lags the gaseous disk to a similar extent as
the rest of the halo, indicating that it does not correspond to a canonical
thick disk. Its properties are inconsistent with those of tidal debris
originating from the Giant Stellar Stream merger event. Moreover, the halo is
chemically distinct from the phase-mixed component previously identified along
the minor axis (i.e., away from the disk), implying contributions from
different formation channels. These metal-rich halo stars provide direct
chemodynamical evidence in favor of the previously suggested "kicked-up'' disk
population in M31's inner stellar halo.Comment: Submitted to AJ. Conclusions on page 20. 18 figures, 2 tables, 4
appendice
Elemental abundances in M31: Individual and Coadded Spectroscopic [Fe/H] and [{\alpha}/Fe] throughout the M31 Halo with SPLASH
We present spectroscopic chemical abundances of red giant branch (RGB) stars
in Andromeda (M31), using medium resolution () spectra obtained via
the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo
(SPLASH) survey. In addition to individual chemical abundances, we coadd low
signal-to-noise ratio (S/N) spectra of stars to obtain a high enough to measure
average [Fe/H] and [/Fe] abundances. We obtain individual and coadded
measurements for [Fe/H] and [/Fe] for M31 halo stars, covering a range
of 9--180 kpc in projected radius from the center of M31. With these
measurements, we greatly increase the number of outer halo ( kpc) M31 stars with spectroscopic [Fe/H] and [/Fe], adding
abundance measurements for 45 individual stars and 33 coadds from a pool of an
additional 174 stars. We measure the spectroscopic metallicity ([Fe/H])
gradient, finding a negative radial gradient of for all
stars in the halo, consistent with gradient measurements obtained using
photometric metallicities. Using the first measurements of [/Fe] for
M31 halo stars covering a large range of projected radii, we find a positive
gradient () in [/Fe] as a function of projected
radius. We also explore the distribution in [Fe/H]--[/Fe] space as a
function of projected radius for both individual and coadded measurements in
the smooth halo, and compare these measurements to those stars potentially
associated with substructure. These spectroscopic abundance distributions
highlight the substantial evidence that M31 has had an appreciably different
formation and merger history compared to our own Galaxy.Comment: Submitted to Ap
The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the
first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises
three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black
Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains
extensive targeting information for the two multi-object spectroscopy programs
(MWM and BHM), including input catalogs and selection functions for their
numerous scientific objectives. We describe the production of the targeting
databases and their calibration- and scientifically-focused components. DR18
also includes ~25,000 new SDSS spectra and supplemental information for X-ray
sources identified by eROSITA in its eFEDS field. We present updates to some of
the SDSS software pipelines and preview changes anticipated for DR19. We also
describe three value-added catalogs (VACs) based on SDSS-IV data that have been
published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.Comment: Accepted to ApJ
The eighteenth data release of the Sloan Digital Sky Surveys : targeting and first spectra from SDSS-V
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains extensive targeting information for the two multi-object spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration- and scientifically-focused components. DR18 also includes ~25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.Publisher PDFPeer reviewe
The eighteenth data release of the Sloan Digital Sky Surveys:targeting and first spectra from SDSS-V
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains extensive targeting information for the two multi-object spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration- and scientifically-focused components. DR18 also includes ~25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field