2 research outputs found
HST survey of the Orion Nebula Cluster in the HO 1.4 m absorption band: I. A census of substellar and planetary mass objects
In order to obtain a complete census of the stellar and sub-stellar
population, down to a few M in the Myr old Orion Nebula
Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble
Space Telescope with the F139M and F130N filters. These bandpasses correspond
to the m HO absorption feature and an adjacent line-free continuum
region. Out of detected sources, (about ) appear fainter
than m (Vega mag) in the F130N filter, a brightness corresponding to
the hydrogen-burning limit mass (M) at Myr. Of
these, however, only sources have a negative F130M-139N color index,
indicative of the presence of HO vapor in absorption, and can therefore be
classified as bona-fide M and L dwarfs, with effective temperatures T K at an assumed Myr cluster age. On our color-magnitude diagram, this
population of sources with HO absorption appears clearly distinct from the
larger background population of highly reddened stars and galaxies with
positive F130M-F139N color index, and can be traced down to the sensitivity
limit of our survey, m, corresponding to a Myr old
M, planetary mass object under about 2 magnitudes of visual
extinction. Theoretical models of the BT-Settl family predicting substellar
isochrones of and Myr (down to M) fail to reproduce
the observed HO color index at MM. We perform a
Bayesian analysis to determine extinction, mass and effective temperature of
each sub-stellar member of our sample, together with its membership
probability.Comment: Accepted for publication in the Astrophysical Journal. The resolution
of several figures has been downgraded to comply with the size limit of arXiv
submission
StraKLIP: A Novel Pipeline for Detection and Characterization of Close-in Faint Companions through the Karhunen-Loéve Image Processing Algorithm
International audienceWe present a new pipeline developed to detect and characterize faint astronomical companions at small angular separation from the host star using sets of wide-field imaging observations not specifically designed for high-contrast imaging analysis. The core of the pipeline relies on Karhunen-Loéve truncated transformation of the reference point-spread function (PSF) library to perform PSF subtraction and identify candidates. Tests of reliability of detections and characterization of companions are made through simulation of binaries and generation of receiver operating characteristic curves for false-positive/true-positive analysis. The algorithm has been successfully tested on large HST/ACS and WFC3 data sets acquired for two HST Treasury Programs on the Orion Nebula Cluster. Based on these extensive numerical experiments we find that, despite being based on methods designed for observations of a single star at a time, our pipeline performs very well on mosaic space-based data. In fact, we are able to detect brown-dwarf-mass companions almost down to the planetary-mass limit. The pipeline is able to reliably detect signals at separations as close as ≳0.″1 with a completeness of ≳10%, or ~0.″2 with a completeness of ~30%. This approach can potentially be applied to a wide variety of space-based imaging surveys, from data in the existing HST archive to near-future JWST mosaics and future wide-field Roman images