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 Hubble Space Telescope/Advanced Cam...
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| Format: | Article |
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IOP Publishing
2023-01-01
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| Series: | The Astronomical Journal |
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| Online Access: | https://doi.org/10.3847/1538-3881/aca9cd |
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| author | Ivanna Escala Amanda C. N. Quirk Puragra Guhathakurta Karoline M. Gilbert J. Leigh Wojno Lara Cullinane Benjamin F. Williams Julianne Dalcanton |
| author_facet | Ivanna Escala Amanda C. N. Quirk Puragra Guhathakurta Karoline M. Gilbert J. Leigh Wojno Lara Cullinane Benjamin F. Williams Julianne Dalcanton |
| author_sort | Ivanna Escala |
| collection | DOAJ |
| description | 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 Hubble Space Telescope/Advanced Camera for Surveys photometry, from the Panchromatic Hubble Andromeda Treasury survey, with Keck/DEIMOS spectra, from the Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo survey. The resulting sample of 3512 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 ∼73% stars have a high likelihood of belonging to the disk and ∼14% to the halo. Although stellar halos are typically thought to be metal-poor, the kinematically identified halo contains a significant population of stars (∼29%) with disk-like metallicity ([Fe/H] _phot ∼ −0.10). 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. |
| first_indexed | 2024-03-12T04:37:04Z |
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| id | doaj.art-8796b2e8619f43fb9b526996c105b0cf |
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| issn | 1538-3881 |
| language | English |
| last_indexed | 2024-03-12T04:37:04Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astronomical Journal |
| spelling | doaj.art-8796b2e8619f43fb9b526996c105b0cf2023-09-03T09:55:18ZengIOP PublishingThe Astronomical Journal1538-38812023-01-0116527510.3847/1538-3881/aca9cdResolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major AxisIvanna Escala0https://orcid.org/0000-0002-9933-9551Amanda C. N. Quirk1https://orcid.org/0000-0001-8481-2660Puragra Guhathakurta2https://orcid.org/0000-0001-8867-4234Karoline M. Gilbert3https://orcid.org/0000-0003-0394-8377J. Leigh Wojno4https://orcid.org/0000-0002-3233-3032Lara Cullinane5https://orcid.org/0000-0001-8536-0547Benjamin F. Williams6https://orcid.org/0000-0002-7502-0597Julianne Dalcanton7https://orcid.org/0000-0002-1264-2006Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA ; iescala@carnegiescience.edu; The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101, USADepartment of Astronomy, Columbia University , 538 West 120th Street, New York, NY 10027, USA; UCO/Lick Observatory, Department of Astronomy & Astrophysics, University of California Santa Cruz , 1156 High Street, Santa Cruz, CA 95064, USAUCO/Lick Observatory, Department of Astronomy & Astrophysics, University of California Santa Cruz , 1156 High Street, Santa Cruz, CA 95064, USASpace Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; The William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USAThe William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA; Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, GermanyThe William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USADepartment of Astronomy, University of Washington , Box 351580, Seattle, WA 98195, USADepartment of Astronomy, University of Washington , Box 351580, Seattle, WA 98195, USA; Center for Computational Astrophysics, Flatiron Institute , 162 5th Avenue, New York, NY 10010, USAStellar 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 Hubble Space Telescope/Advanced Camera for Surveys photometry, from the Panchromatic Hubble Andromeda Treasury survey, with Keck/DEIMOS spectra, from the Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo survey. The resulting sample of 3512 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 ∼73% stars have a high likelihood of belonging to the disk and ∼14% to the halo. Although stellar halos are typically thought to be metal-poor, the kinematically identified halo contains a significant population of stars (∼29%) with disk-like metallicity ([Fe/H] _phot ∼ −0.10). 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.https://doi.org/10.3847/1538-3881/aca9cdGalaxy stellar disksAndromeda GalaxyGalaxy formationGalaxy stellar contentStellar kinematicsStellar abundances |
| spellingShingle | Ivanna Escala Amanda C. N. Quirk Puragra Guhathakurta Karoline M. Gilbert J. Leigh Wojno Lara Cullinane Benjamin F. Williams Julianne Dalcanton Resolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis The Astronomical Journal Galaxy stellar disks Andromeda Galaxy Galaxy formation Galaxy stellar content Stellar kinematics Stellar abundances |
| title | Resolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis |
| title_full | Resolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis |
| title_fullStr | Resolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis |
| title_full_unstemmed | Resolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis |
| title_short | Resolved SPLASH Chemodynamics in Andromeda’s PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis |
| title_sort | resolved splash chemodynamics in andromeda s phat stellar halo and disk on the nature of the inner halo along the major axis |
| topic | Galaxy stellar disks Andromeda Galaxy Galaxy formation Galaxy stellar content Stellar kinematics Stellar abundances |
| url | https://doi.org/10.3847/1538-3881/aca9cd |
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