What Is Missing from the Local Stellar Halo?
The Milky Way’s stellar halo, which extends to >100 kpc, encodes the evolutionary history of our Galaxy. However, most studies of the halo to date have been limited to within a few kiloparsecs of the Sun. Here, we characterize differences between this local halo and the stellar halo in its entire...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ad19ca |
| _version_ | 1797268448023150592 |
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| author | Katherine Sharpe Rohan P. Naidu Charlie Conroy |
| author_facet | Katherine Sharpe Rohan P. Naidu Charlie Conroy |
| author_sort | Katherine Sharpe |
| collection | DOAJ |
| description | The Milky Way’s stellar halo, which extends to >100 kpc, encodes the evolutionary history of our Galaxy. However, most studies of the halo to date have been limited to within a few kiloparsecs of the Sun. Here, we characterize differences between this local halo and the stellar halo in its entirety. We construct a composite stellar halo model by combining observationally motivated N -body simulations of the Milky Way’s nine most massive disrupted dwarf galaxies that account for almost all of the mass in the halo. We find that (i) the representation by mass of different dwarf galaxies in the local halo compared to the whole halo can be significantly overestimated (e.g., the Helmi streams) or underestimated (e.g., Cetus) and (ii) properties of the overall halo (e.g., net rotation) inferred via orbit integration of local halo stars are significantly biased because, for example, highly retrograde debris from Gaia-Sausage-Enceladus is missing from the local halo. Therefore, extrapolations from the local to the global halo should be treated with caution. From analysis of a sample of 11 Milky Way–like simulated halos, we contextualize these results and identify a population of recently accreted (≲5 Gyrs) and disrupted galaxies on high-angular-momenta orbits that are entirely missing from local samples and likely awaiting discovery in the outer halo. Our results motivate the need for surveys of halo stars extending out to the Galaxy’s virial radius. |
| first_indexed | 2024-04-25T01:32:38Z |
| format | Article |
| id | doaj.art-aeb00b3a42274e82951cf53fbb347b0e |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-04-25T01:32:38Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-aeb00b3a42274e82951cf53fbb347b0e2024-03-08T11:12:21ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01963216210.3847/1538-4357/ad19caWhat Is Missing from the Local Stellar Halo?Katherine Sharpe0https://orcid.org/0000-0001-8225-8969Rohan P. Naidu1https://orcid.org/0000-0003-3997-5705Charlie Conroy2https://orcid.org/0000-0002-1590-8551Center for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; kesharpe@berkeley.edu, rnaidu@mit.edu; Department of Astronomy, University of California, Berkeley , 501 Campbell Hall #3411, Berkeley, CA 94720, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; kesharpe@berkeley.edu, rnaidu@mit.edu; MIT Kavli Institute for Astrophysics and Space Research , 77 Massachusetts Avenue, Cambridge, MA 02139, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; kesharpe@berkeley.edu, rnaidu@mit.eduThe Milky Way’s stellar halo, which extends to >100 kpc, encodes the evolutionary history of our Galaxy. However, most studies of the halo to date have been limited to within a few kiloparsecs of the Sun. Here, we characterize differences between this local halo and the stellar halo in its entirety. We construct a composite stellar halo model by combining observationally motivated N -body simulations of the Milky Way’s nine most massive disrupted dwarf galaxies that account for almost all of the mass in the halo. We find that (i) the representation by mass of different dwarf galaxies in the local halo compared to the whole halo can be significantly overestimated (e.g., the Helmi streams) or underestimated (e.g., Cetus) and (ii) properties of the overall halo (e.g., net rotation) inferred via orbit integration of local halo stars are significantly biased because, for example, highly retrograde debris from Gaia-Sausage-Enceladus is missing from the local halo. Therefore, extrapolations from the local to the global halo should be treated with caution. From analysis of a sample of 11 Milky Way–like simulated halos, we contextualize these results and identify a population of recently accreted (≲5 Gyrs) and disrupted galaxies on high-angular-momenta orbits that are entirely missing from local samples and likely awaiting discovery in the outer halo. Our results motivate the need for surveys of halo stars extending out to the Galaxy’s virial radius.https://doi.org/10.3847/1538-4357/ad19caGalaxy stellar halosMilky Way stellar haloGalaxy evolutionMilky Way evolutionthe Milky Way physicsMilky Way formation |
| spellingShingle | Katherine Sharpe Rohan P. Naidu Charlie Conroy What Is Missing from the Local Stellar Halo? The Astrophysical Journal Galaxy stellar halos Milky Way stellar halo Galaxy evolution Milky Way evolution the Milky Way physics Milky Way formation |
| title | What Is Missing from the Local Stellar Halo? |
| title_full | What Is Missing from the Local Stellar Halo? |
| title_fullStr | What Is Missing from the Local Stellar Halo? |
| title_full_unstemmed | What Is Missing from the Local Stellar Halo? |
| title_short | What Is Missing from the Local Stellar Halo? |
| title_sort | what is missing from the local stellar halo |
| topic | Galaxy stellar halos Milky Way stellar halo Galaxy evolution Milky Way evolution the Milky Way physics Milky Way formation |
| url | https://doi.org/10.3847/1538-4357/ad19ca |
| work_keys_str_mv | AT katherinesharpe whatismissingfromthelocalstellarhalo AT rohanpnaidu whatismissingfromthelocalstellarhalo AT charlieconroy whatismissingfromthelocalstellarhalo |