High-resolution Extinction Map in the Direction of the Strongly Obscured Bulge Fossil Fragment Liller 1
Abstract
We used optical images acquired with the Wide Field Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope and near-infrared data from Gemini Multi-conjugate Adaptive Optics System (GeMS)/Gemini South Adaptive Optics Imager (GSAOI) to construct a high-resolution extinction map in the direction of the bulge stellar system Liller 1. In spite of its appearance of a globular cluster, Liller 1 has been recently found to harbor two stellar populations with remarkably different ages, and it is the second complex stellar system with similar properties (after Terzan 5) discovered in the bulge, thus defining a new class of objects: the Bulge Fossil Fragments. Because of its location in the inner bulge of the Milky Way, very close to the Galactic plane, Liller 1 is strongly affected by large and variable extinction. The simultaneous study of both the optical and the near-infrared color-magnitude diagrams revealed that the extinction coefficient RV in the direction of Liller 1 has a much smaller value than commonly assumed for diffuse interstellar medium (RV = 2.5, instead of 3.1), in agreement with previous findings along different light paths to the Galactic bulge. The derived differential reddening map has a spatial resolution ranging from 1″ to 3″ over a field of view of about 90″ × 90″. We found that the absorption clouds show patchy substructures with extinction variations as large as δE(B - V) ~ 0.9 mag. * Based on observations collected with the NASA/ESA HST (Prop. GO 15231), obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Based on observations (Prop. GS-2013-Q-23) obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Based on observations gathered with the ESO-VISTA telescope (program ID 179.B-2002).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2021
- DOI:
- 10.3847/1538-4357/ac0889
- arXiv:
- arXiv:2106.02448
- Bibcode:
- 2021ApJ...917...92P
- Keywords:
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- Globular star clusters;
- Star clusters;
- Reddening law;
- Extinction;
- Galactic bulge;
- 656;
- 1567;
- 1377;
- 505;
- 2041;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in The Astrophysical Journal