The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association
I present infrared spectroscopy of 37 brown dwarf candidates in the Upper Scorpius (Upper Sco) association, 35 of which are classified as young and cool, making them likely members. This sample includes many of the faintest spectroscopically confirmed members ( K = 16–17 mag), which should have mass...
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IOP Publishing
2025-01-01
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| author | K. L. Luhman |
| author_facet | K. L. Luhman |
| author_sort | K. L. Luhman |
| collection | DOAJ |
| description | I present infrared spectroscopy of 37 brown dwarf candidates in the Upper Scorpius (Upper Sco) association, 35 of which are classified as young and cool, making them likely members. This sample includes many of the faintest spectroscopically confirmed members ( K = 16–17 mag), which should have masses down to ∼0.007–0.01 M _⊙ for the range of ages in Upper Sco (7–14 Myr). Using my updated membership catalog for Upper Sco, I have estimated the initial mass function (IMF) for a field in the center of the association that encompasses ∼80% of the known members. I have derived IMFs in the same manner for previous membership samples in three other star-forming populations, consisting of IC 348, Taurus, and Chameleon I. When using logarithmic mass bins, the substellar IMFs for Upper Sco and the other young regions are roughly flat down to the completeness limits of ∼0.01 M _⊙ . These IMFs are broadly similar to mass functions recently measured for the solar neighborhood. Finally, I have used W1−W2 colors to search for excess emission from circumstellar disks among the late-type objects in my new census of Upper Sco. I measure an excess fraction of 52/200 for members with spectral types of M6.25–M9.5, which is similar to results from previous membership catalogs. For the L-type members, it is difficult to detect the small W2 excess emission produced by typical disks around brown dwarfs because of the large uncertainties in spectral types, which preclude accurate estimates of the photospheric colors. Thus, W2 photometry provides poor constraints on the presence of disks for the L-type members of Upper Sco. |
| format | Article |
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| institution | OA Journals |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-9b776398ac4646c7ade496defe09c1732025-08-20T02:30:31ZengIOP PublishingThe Astronomical Journal1538-38812025-01-0117011910.3847/1538-3881/add68cThe Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco AssociationK. L. Luhman0https://orcid.org/0000-0003-2822-2951Department of Astronomy and Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA ; kll207@psu.edu; Center for Exoplanets and Habitable Worlds, The Pennsylvania State University , University Park, PA 16802, USAI present infrared spectroscopy of 37 brown dwarf candidates in the Upper Scorpius (Upper Sco) association, 35 of which are classified as young and cool, making them likely members. This sample includes many of the faintest spectroscopically confirmed members ( K = 16–17 mag), which should have masses down to ∼0.007–0.01 M _⊙ for the range of ages in Upper Sco (7–14 Myr). Using my updated membership catalog for Upper Sco, I have estimated the initial mass function (IMF) for a field in the center of the association that encompasses ∼80% of the known members. I have derived IMFs in the same manner for previous membership samples in three other star-forming populations, consisting of IC 348, Taurus, and Chameleon I. When using logarithmic mass bins, the substellar IMFs for Upper Sco and the other young regions are roughly flat down to the completeness limits of ∼0.01 M _⊙ . These IMFs are broadly similar to mass functions recently measured for the solar neighborhood. Finally, I have used W1−W2 colors to search for excess emission from circumstellar disks among the late-type objects in my new census of Upper Sco. I measure an excess fraction of 52/200 for members with spectral types of M6.25–M9.5, which is similar to results from previous membership catalogs. For the L-type members, it is difficult to detect the small W2 excess emission produced by typical disks around brown dwarfs because of the large uncertainties in spectral types, which preclude accurate estimates of the photospheric colors. Thus, W2 photometry provides poor constraints on the presence of disks for the L-type members of Upper Sco.https://doi.org/10.3847/1538-3881/add68cBrown dwarfsL dwarfsStar formationInitial mass functionCircumstellar disksStar forming regions |
| spellingShingle | K. L. Luhman The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association The Astronomical Journal Brown dwarfs L dwarfs Star formation Initial mass function Circumstellar disks Star forming regions |
| title | The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association |
| title_full | The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association |
| title_fullStr | The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association |
| title_full_unstemmed | The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association |
| title_short | The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association |
| title_sort | initial mass function of stars and brown dwarfs in the upper sco association |
| topic | Brown dwarfs L dwarfs Star formation Initial mass function Circumstellar disks Star forming regions |
| url | https://doi.org/10.3847/1538-3881/add68c |
| work_keys_str_mv | AT klluhman theinitialmassfunctionofstarsandbrowndwarfsintheupperscoassociation AT klluhman initialmassfunctionofstarsandbrowndwarfsintheupperscoassociation |