The young stellar population at the center of NGC 205
Journal
Date Issued
2009
Author(s)
Monaco, L.
•
Saviane, I.
•
•
•
•
Federici, L.
•
Fusi Pecci, F.
•
Abstract
Context: NGC 205 is a peculiar dwarf elliptical galaxy hosting in its center a population of young blue stars. Their origin is still matter of debate, the central fresh star formation activity possibly being related to dynamical interactions between NGC 205 and M 31.
Aims: The star formation history in the central 30´´ (~120 pc) around the NGC 205 central nucleus is investigated in order to obtain clues to the origin of the young stellar population.
Methods: Deep HST/ACS CCD photometry is compared with theoretical isochrones and luminosity functions to characterize the stellar content of the region under study and compute the recent SF rate.
Results: Our photometry reveals a previously undetected blue plume of young stars clearly distinguishable down to I≃ 26. Our analysis suggests that 1.9 × 105 M_⊙ were produced between approximately 62 Myr and 335 Myr ago in the NGC 205 inner regions, with a latest minor episode occurring ~25 Myr ago. This implies a star formation rate of ~7× 10-4 M_⊙/yr over this period.
Conclusions: The excellent fit of the observed luminosity function of young main sequence stars obtained with a model having a constant star formation rate argues against a tidally triggered star formation activity over the last ~300 Myr. Rather, a constant SF may be consistent with NGC 205 being on its first interaction with M 31.
Aims: The star formation history in the central 30´´ (~120 pc) around the NGC 205 central nucleus is investigated in order to obtain clues to the origin of the young stellar population.
Methods: Deep HST/ACS CCD photometry is compared with theoretical isochrones and luminosity functions to characterize the stellar content of the region under study and compute the recent SF rate.
Results: Our photometry reveals a previously undetected blue plume of young stars clearly distinguishable down to I≃ 26. Our analysis suggests that 1.9 × 105 M_⊙ were produced between approximately 62 Myr and 335 Myr ago in the NGC 205 inner regions, with a latest minor episode occurring ~25 Myr ago. This implies a star formation rate of ~7× 10-4 M_⊙/yr over this period.
Conclusions: The excellent fit of the observed luminosity function of young main sequence stars obtained with a model having a constant star formation rate argues against a tidally triggered star formation activity over the last ~300 Myr. Rather, a constant SF may be consistent with NGC 205 being on its first interaction with M 31.
Volume
502
Issue
2
Start page
L9
Issn Identifier
0004-6361
Ads BibCode
2009A&A...502L...9M
Rights
open.access
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