We report the results of the first deep, wide-field, near-infrared methane imaging survey of the Rho Ophiuchi cloud core to search for T dwarfs. Among the 6587 objects detected, 22 were identified as T dwarf candidates. Brown dwarf models indicate that at the age and distance of the Rho Ophiuchi cloud, these T dwarf candidates have masses between 1 and 2 Jupiter masses. If confirmed as genuine T dwarfs, these objects would be the youngest, lowest mass, and lowest gravity free-floating objects ever directly observed. The existence of these candidates suggests that the initial mass function of the Rho Ophiuchi cloud extends well into the regime of planetary mass objects. A large fraction (59% +/- 16%) of our T dwarf candidates appear to be surrounded by circumstellar disks, and thus represent the lowest mass objects yet found to harbor circumstellar disks.
We report the discovery of two methane dwarfs in the dark cloud L 1688 of the Rho Oph star-forming region. The two objects were among the T dwarf candidates with possible methane absorption and cool atmospheres, as diagnosed by infrared colors using deep WIRCam/CFHT HK plus CH4ON images, and IRAC/Spitzer c2d data. Follow-up spectroscopic observations with the FLAMINGOS-2/Gemini South confirmed the methane absorption at 1.6 micron. Compared with spectral templates of known T dwarfs in the field, i.e., of the old populations, Oph J162738-245240 (Oph-T3) is a T0/T1 type, whereas Oph J162645-24194…
Using the IRAC images from the Spitzer c2d program, we have made a survey of mid-infrared outflows in the rho Ophiuchi molecular cloud. Extended objects that have prominent emission in IRAC channel 2 (4.5 micron) compared to IRAC channel 1 (3.6 micron) and stand out as green objects in the three-color images (3.6 micron in blue, 4.5 micron in green, 8.0 micron in red) are identified as mid-infrared outflows. As a result, we detected 13 new outflows in the rho Ophiuchi molecular cloud that have not been previously observed in optical or near-infrared. In addition, at the positions of previously…
SONYC - Substellar Objects in Nearby Young Clusters - is a survey program to investigate the frequency and properties of brown dwarfs down to masses below the Deuterium burning limit in nearby star forming regions. In this second paper, we present results on the ~1 Myr old cluster Rho Ophiuchi, combining our own deep optical and near-infrared imaging using Subaru with photometry from the 2-Micron All Sky Survey and the Spitzer Space Telescope. Of the candidates selected from iJKs photometry, we have confirmed three -- including a new brown dwarf with a mass close to the Deuterium limit -- as l…
We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3 square degrees of the Rho Ophiuchi star forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased towards particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function.We have obtained over 300 optical spectra to help identify 135 association members based on the presence of H-alpha in emission, lithium absorption, X-ray …
We aim to take a census of molecular hydrogen emission line objects (MHOs) in the Rho Ophiuchi molecular cloud and to make the first systematic proper motion measurements of these objects in this region. Deep H2 near-infrared imaging is performed to search for molecular hydrogen emission line objects. Multi-epoch data are used to derive the proper motions of the features of these objects, and the lengths and opening angles of the molecular hydrogen outflows. Our imaging covers an area of about 0.11 deg2 toward the L1688 core in the Rho Ophiuchi molecular cloud. In total, six new MHOs are disco…
Star formation in molecular clouds can be triggered by the dynamical action of winds from massive stars. Furthermore, X-ray and UV fluxes from massive stars can influence the life time of surrounding circumstellar disks. We present the results of a 53 ks XMM-Newton observation centered on the Rho Ophiuchi A+B binary system. Rho Ophiiuchi lies in the center of a ring of dust, likely formed by the action of its winds. This region is different from the dense core of the cloud (L1688 Core F) where star formation is at work. X-rays are detected from Rho Ophiuchi as well as a group of surrounding X-…
The infrared [Ne II] and [Ne III] fine structure lines at 12.81um and 15.55um are predicted to trace the circumstellar disk gas subject to X-ray heating and ionization. We investigate the origin of these lines by comparing observations with models of X-ray irradiated disks and by searching for empirical correlations between the line luminosities and stellar and circumstellar parameters. We measure neon line fluxes and X-ray luminosities for 28 young stellar objects in the Rho Ophiuchi star formation region for which good quality infrared spectra and X-ray data have been obtained, the former wi…
X-rays from very young stars are powerful probes to investigate the mechanisms at work in the very first stages of the star formation and the origin of X-ray emission in very young stars. We present results from a 500 ks long observation of the Rho Ophiuchi cloud with a XMM-Newton large program named DROXO, aiming at studying the X-ray emission of deeply embedded Young Stellar Objects (YSOs). The data acquired during the DROXO program were reduced with SAS software, and filtered in time and energy to improve the signal to noise of detected sources; light curves and spectra were obtained. We de…
We present a general method for identifying the pre-main-sequence population of any star-forming region, unbiased with respect to the presence or absence of disks, in contrast to samples selected primarily via their mid-infrared emission from Spitzer surveys. We have applied this technique to a new, deep, wide-field, near-infrared imaging survey of the Rho Ophiuchi cloud core to search for candidate low mass members. In conjunction with published Spitzer IRAC photometry, and least squares fits of model spectra (COND, DUSTY, NextGen, and blackbody) to the observed spectral energy distributions,…
SONYC - Substellar Objects in Nearby Young Clusters - is a survey program to investigate the frequency and properties of substellar objects with masses down to a few times that of Jupiter in nearby star-forming regions. For the ~1Myr old rho Ophiuchi cluster, in our earlier paper we reported deep, wide-field optical and near-infrared imaging using Subaru, combined with 2MASS and Spitzer photometry, as well as follow-up spectroscopy confirming three likely cluster members, including a new brown dwarf with a mass close to the deuterium-burning limit. Here we present the results of extensive new …
Recent observations of the Rho Ophiuchi cluster with the Herschel Space Observatory allow us to probe the spectral energy distribution (SED) of the brown dwarf population in the far-IR, where the disk emission peaks. We performed aperture photometry at 70, 100, and 160 micron, and constructed SEDs for all previously known brown dwarfs detected. These were complemented with ancillary photometry at shorter wavelengths. We compared the observed SEDs to a grid of synthetic disks produced with the radiative transfer code MCFOST, and used the relative figure of merit estimated from the Bayesian infe…
We report here our search for molecular outflows from young very low mass stars and brown dwarfs in Taurus and rho Ophiuchi. Using the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter-wave Astronomy (CARMA), we have observed 4 targets at 1.3 mm wavelength (230 GHz) to search for CO J=2-->1 outflows. A young very low mass star MHO 5 (in Taurus) with an estimated mass of 90 M_J, which is just above the hydrogen-burning limit, shows two gas lobes that are likely outflows. While the CO map of MHO 5 does not show a clear structure of outflow, possibly due to environment g…
We present a systematic search for Fe Kalpha emission from young stellar objects of the rho Ophiuchi star forming region observed in the Deep Rho Ophiuchi XMM-Newton Observation (DROXO).
We present the results of CO (J=3-2) and CO (J=1-0) mapping observations toward the active cluster forming clump, L1688, in the rho Ophiuchi molecular cloud. From the CO (J=3-2) and CO (J=1-0) data cubes, we identify five outflows, whose driving sources are VLA 1623, EL 32, LFAM 26, EL 29, and IRS 44. Among the identified outflows, the most luminous outflow is the one from the prototypical Class 0 source, VLA 1623. We also discover that the EL 32 outflow located in the Oph B2 region has very extended blueshifted and redshifted lobes with wide opening angles. This outflow is most massive and ha…
We present new ATCA observations at 3.3 mm of 27 young stellar objects in the rho-Oph young cluster. 25 of these sources have been detected. We analyze the sub-millimeter and millimeter SED for a subsample of 17 isolated class II protoplanetary disks and derive constraints on the grain growth and total dust mass in the disk outer regions. All the disks in our sample show a mm slope of the SED which is significantly shallower than the one observed for the ISM at these long wavelengths. This indicates that 1) class II disks in Ophiuchus host grains grown to mm/cm-sizes in their outer regions, 2)…
Using the archive data of the H13CO+ (J=1-0) line emission taken with the Nobeyama 45 m radio telescope with a spatial resolution of about 0.01pc, we have identified 68 dense cores in the central dense region of the rho Ophiuchi main cloud. The H13CO+ data also indicates that the fractional abundance of H13CO+ relative to H2 is roughly inversely proportional to the square root of the H2 column density with a mean of 1.72 x 10^{-11}. The mean radius, FWHM line width, and LTE mass of the identified cores are estimated to be 0.045 +- 0.011 pc, 0.49 +- 0.14 km/s, and 3.4 +- 3.6 Msolar, respectivel…
We aim at performing a kinematic census of young stellar objects (YSOs) in the Rho Ophiuchi F core and partially in the E core of the L1688 dark cloud. We run a proper motion program at the ESO New Technology Telescope (NTT) with the Son of ISAAC (SOFI) instrument over nine years in the near-infrared. We complemented these observations with various public image databases to enlarge the time base of observations and the field of investigation to 0.5 deg X 0.5 deg. We derived positions and proper motions for 2213 objects. From these, 607 proper motions were derived from SOFI observations with a …
(Abridged) We present a study of the disk population in L1688, the densest and youngest region in Ophiuchus, and we compare it with other nearby regions of different age, namely Lupus, Chamaeleon I, Corona Australis, Taurus and Upper Scorpius. We select our L1688 sample using a combination of criteria (ALMA data, Gaia, optical/near-IR spectroscopy) and determine stellar and disk properties, specifically stellar mass (Mstar), average population age, mass accretion rate (Macc) and disk dust mass (Mdust). a) In L1688 the relations between Macc and Mstar, Mdust and Mstar, and Macc and Mdust have a…
We report the discovery of a young planetary-mass brown dwarf in the rho Oph cloud core. The object was identified as such with the aid of a 1.5-2.4 micron low-resolution spectrum obtained using the NIRC instrument on the Keck I telescope. Based on the COND model, the observed spectrum is consistent with a reddened (Av ~ 15-16) brown dwarf whose effective temperature is in the range 1200-1800 K. For an assumed age of 1 Myr, comparison with isochrones further constrains the temperature to ~ 1400 K and suggests a mass of ~ 2-3 Jupiter masses. The inferred temperature is suggestive of an early T …
We report here our latest search for molecular outflows from young brown dwarfs and very low-mass stars in nearby star-forming regions. We have observed three sources in Taurus with the Submillimeter Array and the Combined Array for Research in Millimeter-wave Astronomy at 230 GHz frequency to search for CO J=2-1 outflows. We obtain a tentative detection of a redshifted and extended gas lobe at about 10 arcsec from the source GM Tau, a young brown dwarf in Taurus with an estimated mass of 73 M_J, which is right below the hydrogen-burning limit. No blueshifted emission around the brown dwarf po…
SONYC, short for "Substellar Objects in Nearby Young Clusters", is a survey program to provide a census of the substellar population in nearby star forming regions. We have conducted deep optical and near-infrared photometry in five young regions (NGC1333, rho Ophiuchi, Chamaeleon-I, Upper Sco, and Lupus-3), combined with proper motions, and followed by extensive spectroscopic campaigns with Subaru and VLT, in which we have obtained more than 700 spectra of candidate low-mass objects. We have identified and characterized more than 60 new substellar objects, among them a handful of objects with…
