Valdivielso, L.; Martín, E. L.; Bouy, H.; Solano, E.; Drew, J. E.; Greimel, R.; Gutiérrez, R.; Unruh, Y. C.; Vink, J. S.
Bibliographical reference
Astronomy and Astrophysics, Volume 497, Issue 3, 2009, pp.973-981
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4
2009
Journal
Citations
15
Refereed citations
12
Description
Context: The main goal of this paper is to prove that accreting very
low-mass stars and brown dwarfs can be identified in IPHAS, an Hα
emission survey of the northern Milky Way. Full exploitation of the
IPHAS database and a future extension of it in the southern hemisphere
will be useful in identifying very low-mass accreting objects near to
and far from well-known star-forming regions. Aims: We have used
Virtual Observatory tools to cross-match the IPHAS catalogue with the
2MASS catalogue. We defined photometric criteria to identify Hα
emission sources with near-infrared colours similar to those of known
young very low-mass stars and brown dwarfs. 4000 candidates were
identified that met our criteria over an area of 1600 square degrees. We
present low-resolution optical spectra of 113 candidates. Spectral types
have been derived for the 33 candidates that have spectroscopically
confirmed Hα emission, negligible reddening and spectral class M.
We have also measured Hα emission and investigated the NaI doublet
(818.3 nm, 819.5 nm) in these 33 objects. Methods: We confirm
that 33 IPHAS candidates have strong Hα emission indicative of
disc accretion for their spectral type. Twenty-three of them have
spectral class M4 or later, of which ten have classes in the range
M5.5-M7.0 and could thus be very young brown dwarfs. Many objects also
have a weak NaI doublet, an indication of low surface gravity. Results: IPHAS provides a very valuable database for identifying
accreting very low-mass stars and brown dwarfs. Virtual Observatory
tools provide an efficient method for identifying these objects over
large areas of the sky. Based on our success rate of 23 Hα
emission objects with spectral type in the range M4-M7 out of 113
candidates with spectroscopic follow-up, we estimate that there could be
hundreds of such objects in the full IPHAS survey.