HST/STIS spectroscopy of the optical outflow from DG Tau: structure and kinematics on sub-arcsecond scales

By F. Bacciotti, R. Mundt, T. Ray, J. Eisloeffel, J. Solf, M. C. D. I. F. A. Studies, Dublin, Ireland, M. F. Astronomie, Heidelberg and 4 more. 2000

168 citations recorded by the source corpus.

We have carried out a spatio-kinematic study of the outflow from the classical T Tauri star DG Tau using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). A series of seven spatially offset long-slit spectra spaced by 0.07'' were obtained along the axis of the outflow to build up a 3-D intensity-velocity ``cube'' in various forbidden emission lines (FELs) and Ha. Here we present high spatial resolution synthetic line images close to the star in distinct radial velocity intervals (from ~ +50 km/s to ~ -450 km/s in four bins, each ~ 125 km/s wide). The lowest velocity emission is also examined in finer detail (from +60 km/s to -70 km/s in five bins ~ 25 km/s wide). We have found that the highest velocity and most highly collimated component, i.e. the jet, can be traced from DG Tau to a distance D ~ 0.7''. The jet is on the axis of a pear-shaped limb-brightened bubble which extends between 0.4'' and 1.5'' from the source and which we interpret as a bow shock. Other condensations are seen close to the star indicating ongoing temporal variations in the flow. The low-velocity component of the outflow is found to be spatially wide close to the source (~ 0.2'' at D=0.2''), in contrast to the high velocity jet (width<~ 0.1''). We have also found evidence to suggest that the density increases longitudinally with proximity to the source and also laterally towards the flow axis. Thus, at least in the case of DG Tau, the flow becomes gradually denser as it increases in velocity and becomes more collimated. Our observations show a continous bracketing of the higher speed central flow within the lower speed, less collimated, broader flow, down to the lowest velocity scales. This suggests that the low and high velocity FELs in the highly active T Tauri star DG Tau are intimately related.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

On the Evolutionary Status of Class I Stars and Herbig-Haro Energy Sources in Taurus-Auriga (2004, background): “The low-velocity emission is usually spatially coincident with the stellar position, while the high-velocity emission appears spatially extended, often in the form of a wellcollimated jet (e.g., Mundt et al. 1987; Lavalley et al. 1997; Bacciotti et al. 2000).”
AN OPTICAL SPECTROSCOPIC STUDY OF T TAURI STARS. I. PHOTOSPHERIC PROPERTIES (2014, background): “DG Tau DG Tau is the source of a famous and wellstudied jet (e.g. Eislöffel & Mundt 1998; Bacciotti et al. 2000).”
MHD simulations of jet acceleration from Keplerian accretion disks - The effects of disk resistivity (2007, background): “The size of the launching region measured in our simulations (from 0.1 to 1 AU) is consistent with the estimates derived from observations (Bacciotti et al. 2000).”
Photoevaporation of Circumstellar Disks around Young Stars (2004, unknown): “Increasingly, however, high resolution instruments, such as the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope, are resolving nearby systems (e.g., Bacciotti et al. 2000, 2002).”
Magnetocentrifugal Launching of Jets from Accretion Disks. II. Inner Disk-driven Winds (2003, background): “A recent example of such observations is that of Bacciotti et al. (2000).”
Launching of conical winds and axial jets from the disc–magnetosphere boundary: axisymmetric and 3D simulations (2009, background): “High-resolution observations of CTTSs show that the outflows often have an ‘onion-skin’ structure, with better-collimated, higher velocity outflows in the axial region and less-collimated, lower velocity outflows at a larger distance from the axis (Bacciotti et al. 2000).”
Heating and Ionization of X-Winds (2001, methodology): “…than 25 AU, observations with an angular resolution signiÐcantly better than are required for sources at a distance of 150 pc.0A.15 Recent measurements with HST (Bacciotti et al. 2000) and with an adaptive optics system on the CHFT (Dougados et al. 2000) have begun to probe jets on this scale.”
Which jet launching mechanism(s) in T Tauri stars (2006, background): “Could the samextendeddisc winds also explain the highvelocity component (HVC) at 200-400 km s−1 observed in forbidden lines closer to the jet axis (e.g. Bacciotti et al. 2000), or is another ejection process necessary ?”
Rotation of Jets from Young Stars: New Clues from the Hubble Space Telescope Imaging Spectrograph (2003, background): “The high velocity component (HVC), which is located much closer to the jet axis and gives rise to the emission peak (Bacciotti et al. 2000), appears not to be spatially resolved in our spectra.”
HERBIG-HARO FLOWS: Probes of Early Stellar Evolution (2001, background): “Further details are given in Bacciotti et al. (1996, 1997, 1999, 2000) and Bacciotti & Eislöffel (1999).”
Theory of Star Formation (2007, background): “…fact indicate that a lower-velocity [∼ (10 − 50) km s−1] wind component is present near the source, surrounding the high-velocity flow of a few 100 km s−1 that emerges as the large-scale jet (Hartigan, Edwards, & Ghandour, 1995; Hirth, Mundt, & Solf, 1997; Bacciotti et al., 2000; Pyo et al., 2005).”