85 research outputs found

    Molecular outflows in the young open cluster IC348

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    We present a wide-field survey of the young open cluster IC348 for molecular H2 outflows. Outflow activity is only found at its south-western limit, where a new subcluster of embedded sources is in an early phase of its formation. If the IC348 cluster had been built up by such subclusters forming at different times, this could explain the large age-spread that Herbig (1998) found for the IC348 member stars. In addition to several compact groups of H2 knots, our survey reveals a large north-south oriented outflow, and we identify the newly discovered far-infrared and mm-object IC348MMS as its source. New deep images in the 1-0 S(1) line of molecular hydrogen trace the HH211 jet and counterjet as highly-collimated chains of knots, resembling the interferometric CO and SiO jets. This jet system appears rotated counter-clockwise by about 3 degrees with respect to the prominent H2 bow shocks. Furthermore, we resolve HH211-mm as a double point-like source in the mm-continuum.Comment: 10 pages, 9 figures, accepted for publication in Ap

    The Search for Signatures Of Transient Mass Loss in Active Stars

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    The habitability of an exoplanet depends on many factors. One such factor is the impact of stellar eruptive events on nearby exoplanets. Currently this is poorly constrained due to heavy reliance on solar scaling relationships and a lack of experimental evidence. Potential impacts of Coronal Mass Ejections (CMEs), which are a large eruption of magnetic field and plasma from a star, are space weather and atmospheric stripping. A method for observing CMEs as they travel though the stellar atmosphere is the type II radio burst, and the new LOw Frequency ARray (LOFAR) provides a means for detection. We report on 15 hours of observation of YZ Canis Minoris (YZ CMi), a nearby M dwarf flare star, taken in LOFAR's beam-formed observation mode for the purposes of measuring transient frequency-dependent low frequency radio emission. The observations utilized Low-Band Antenna (10-90 MHz) or High-Band Antenna (110-190 MHz) for five three-hour observation periods. In this data set, there were no confirmed type II events in this frequency range. We explore the range of parameter space for type II bursts constrained by our observations Assuming the rate of shocks is a lower limit to the rate at which CMEs occur, no detections in a total of 15 hours of observation places a limit of ÎœtypeII<0.0667\nu_{type II} < 0.0667 shocks/hr ≀ΜCME \leq \nu_{CME} for YZ CMi due to the stochastic nature of the events and limits of observational sensitivity. We propose a methodology to interpret jointly observed flares and CMEs which will provide greater constraints to CMEs and test the applicability of solar scaling relations

    The Optical Proper Motions of HH 7-11 and Cep E (HH 377)

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    A key ingredient in understanding the dynamics of stellar outflows is their proper motion. We have used optical images in the [SII] emission at 6717/31 A and the red Digitized Palomar Observatory Sky Survey (DSS) plates to determine the proper motion of HH 7-11 system and the optical knot of Cep E (HH 377). The DSS plate measurements span nearly 37 years for both HH 7-11 and HH 377 and have wide field of view, which allows an accurate determination of the proper motions despite their relatively low angular resolution. The optical images, with higher angular resolution, cover a shorter period of 7 and 4 years, respectively, and have been used to complement the DSS measurements. From the DSS plates we have found that HH 377 has a proper motion of 0.031 +/- 0.003 arcsec/yr with a PA = 206 arcdeg, i.e. moving away from IRAS 230111+63, that at a distance of 730 pc corresponds to a tangential velocity of 107 +/- 14 km/s. The values obtained from the optical images are consistent with these measurements. Similarly, the proper motions of HH 7-11 range from 0.015 +/- 0.009 (HH 9) to 0.044 +/- 0.007 (HH 11) arcsec/yr, and the flow is moving away from SVS 13 with a mean PA = 136 arcdeg. At a distance of 330 pc, these motions correspond to tangential velocities of 25 - 70 km/s, i.e. comparable to the original values obtained by Herbig & Jones (1983). The measurements from the optical CCD [SII] images are again consistent with these motions, although in detail there are some difference, particularly for HH 7 and HH 10.Comment: 18 pages, 6 Figures (jpgs because of their size

    Two Bipolar Outflows and Magnetic Fields in a Multiple Protostar System, L1448 IRS 3

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    We performed spectral line observations of CO J=2-1, 13CO J=1-0, and C18O J=1-0 and polarimetric observations in the 1.3 mm continuum and CO J=2-1 toward a multiple protostar system, L1448 IRS 3, in the Perseus molecular complex at a distance of ~250 pc, using the BIMA array. In the 1.3 mm continuum, two sources (IRS 3A and 3B) were clearly detected with estimated envelope masses of 0.21 and 1.15 solar masses, and one source (IRS 3C) was marginally detected with an upper mass limit of 0.03 solar masses. In CO J=2-1, we revealed two outflows originating from IRS 3A and 3B. The masses, mean number densities, momentums, and kinetic energies of outflow lobes were estimated. Based on those estimates and outflow features, we concluded that the two outflows are interacting and that the IRS 3A outflow is nearly perpendicular to the line of sight. In addition, we estimated the velocity, inclination, and opening of the IRS 3B outflow using Bayesian statistics. When the opening angle is ~20 arcdeg, we constrain the velocity to ~45 km/s and the inclination angle to ~57 arcdeg. Linear polarization was detected in both the 1.3 mm continuum and CO J=2-1. The linear polarization in the continuum shows a magnetic field at the central source (IRS 3B) perpendicular to the outflow direction, and the linear polarization in the CO J=2-1 was detected in the outflow regions, parallel or perpendicular to the outflow direction. Moreover, we comprehensively discuss whether the binary system of IRS 3A and 3B is gravitationally bound, based on the velocity differences detected in 13CO J=1-0 and C18O J=1-0 observations and on the outflow features. The specific angular momentum of the system was estimated as ~3e20 cm^2/s, comparable to the values obtained from previous studies on binaries and molecular clouds in Taurus.Comment: ApJ accepted, 20 pages, 2 tables, 10 figure

    Highly Collimated Jets and Wide-Angle Outflows in HH46/47: New Evidence from Spitzer IR Images

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    We present new details of the structure and morphology of the jets and outflows in HH46/47 as seen in Spitzer infrared images from IRAC and MIPS, reprocessed using the ``HiRes'' deconvolution technique. HiRes improves the visualization of spatial morphology by enhancing resolution (to sub-arcsec levels in IRAC bands) and removing the contaminating side lobes from bright sources. In addition to sharper views of previously reported bow shocks, we have detected: (i) the sharply-delineated cavity walls of the wide-angle biconical outflow, seen in scattered light on both sides of the protostar, (ii) several very narrow jet features at distances 400 AU to 0.1 pc from the star, and, (iii) compact emissions at MIPS 24 micron coincident with the jet heads, tracing the hottest atomic/ionic gas in the bow shocks.Comment: 11 pages, 4 Figures, Accepted for publication in ApJ(Letters

    The 3-Dimensional Structure of HH 32 from GMOS IFU Spetroscopy

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    We present new high resolution spectroscopic observations of the Herbig-Haro object HH 32 from System Verification observations made with the GMOS IFU at Gemini North Observatory. The 3D spectral data covers a 8''.7 x 5''.85 spatial field and 4820 - 7040 Angstrom spectral region centered on the HH~32 A knot complex. We show the position-dependent line profiles and radial velocity channel maps of the Halpha line, as well as line ratio velocity channel maps of [OIII]5007/Halpha, [OI]6300/Halpha, [NII]6583/Halpha, [SII](6716+6730)/Halpha and [SII]6716/6730. We find that the line emission and the line ratios vary significantly on spatial scales of ~1'' and over velocities of ~50 km/s. A ``3/2-D'' bow shock model is qualitatively successful at reproducing the general features of the radial velocity channel maps, but it does not show the same complexity as the data and it fails to reproduce the line ratios in our high spatial resolution maps. The observations of HH 32 A show two or three superimposed bow shocks with separations of ~3'', which we interpret as evidence of a line of sight superposition of two or three working surfaces located along the redshifted body of the HH 32 outflow.Comment: Accepted for Publication in the Astronomical Journal (January 2004

    Detection of Extended Hot Water in the Outflow from NGC 2071

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    We report the results of spectroscopic mapping observations carried out toward a ~1 min x 1 min region within the northern lobe of the outflow from NGC 2071 using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations covered the 5.2-37 um spectral region and have led to the detection of a number of ionic, atomic, and molecular lines, including fine-structure emission of Si+, Fe+, S++, S, the S(0)-S(7) pure rotational lines of H2, the R(3) and R(4) transitions of HD, and at least 11 transitions of H2O. In addition, the 6.2, 7.4, 7.6, 7.9, 8.6 and 11.3 um PAH emission bands were also observed and several transitions of OH were tentatively detected. Most of the detected line transitions were strong enough to map including, for the first time, three transitions of hot H2O. We find that: (1) the water emission is extended; (2) the extended emission is aligned with the outflow; and, (3) the spatial distribution of the water emission generally follows that observed for H2. Based on the measured line intensities, we derive an HD abundance relative to H2 of 1.1-1.8 10^-5 and an H2O number density of 12-2 cm^3. The H2 density in the water-emitting region is not well constrained by our observations, but is likely between 3 10^4 and 10^6 cm^3, yielding an H2O abundance relative to H2 of between 2 10^-5 and 6 10^-4. Future observations planned for the Herschel Space Observatory should greatly improve the density estimate, and thus our knowledge of the H2O abundance, for the water-emitting regions reported here. Finally, we note a possible departure from the H2O ortho-to-para ratio of 3:1 expected for water formed in hot post-shocked gas, suggesting that a significant fraction of the water vapor we detect may arise from H2O sputtered from cold dust grains.Comment: 35 pages, 15 figures, 4 tables, accepted for publication in Ap

    Spatially Resolved Molecular Hydrogen Emission in the Inner 200AU Environments of Classical T Tauri Stars

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    We present 2.0-2.4micron integral field spectroscopy at adaptive optics spatial resolution (~0.''1) obtained with the Near-infrared Integral Field Spectrograph (NIFS) at Gemini North Observatory of six Classical T Tauri stars: T Tau, DG Tau, XZ Tau, HL Tau, RW Aur and HV Tau C. In all cases, the v=1-0 S(1) (2.12 micron) emission is detected at spatially extended distances from the central stars. The bulk of the H_2 emission is typically not spatially coincident with the location of continuum flux. Multiple transitions detected in the K-band spectra show that H_2 level populations are typical of gas in thermal equilibrium with excitation temperatures in the 1800K-2300 K range. Three of the stars have H_2 velocity profiles that are centered at the stellar radial velocity, and three show velocity shifts with respect to the system. Each of the stars studied here show observed excitation temperatures, spatial extents, and kinematics of the H_2 that are most consistent with shock excited emission from the inner regions of the known Herbig-Haro energy flows or from wide-angle winds encompassing the outflows rather than predominantly from UV or X-ray stimulated emission from the central stars. The data presented in this study highlights the sensitivity of adaptive optics-fed integral field spectroscopy for spatially resolving emission line structures in the environments of bright young stars.Comment: 50 pages, 13 Figures. Accepted for publication in the Astrophysical Journal. Full Resolution paper available at: http://www.astro.sunysb.edu/tracy/pubs/Beck07.pd

    A Methane Isolated Planetary Mass Object in Orion

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    We report on the discovery of a free-floating methane dwarf toward the direction of the young star cluster sigma Orionis. Based on the object's far-red optical and near-infrared photometry and spectroscopy, we conclude that it is a possible member of this association. We have named it as S Ori J053810.1-023626 (S Ori 70 is the abridged name). If it is a true member of sigma Orionis, the comparison of the photometric and spectroscopic properties of S Ori 70 with state-of-the-art evolutionary models yields a mass of 3 (+5/-1) Jupiter mass for ages between 1 Myr and 8 Myr. The presence of such a low-mass object in our small search area (55.4 sq. arcmin) would indicate a rising substellar initial mass function in the sigma Orionis cluster even for planetary masses.Comment: Accepted for publication in the ApJ. Twelve pages, figures and tables include