High-contrast Polarimetry Observation of the T Tau Circumstellar Environment

Abstract

We conducted high-contrast polarimetry observations of T Tau in the H-band, using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics instrument mounted on the Subaru Telescope, revealing structures as near as 0 1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebulalike envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearly face-on circumstellar disk of T Tau N is no larger than 0 8, or 117 au, in the northwest, based on the existence of a hole in this direction, and no larger than 0 27, or 40 au, in the south. A new structure, "N5," extends to about 0 42, or 59 au, southwest of the star, and is believed to be part of the disk. We suggest that T Tau S is surrounded by a highly inclined circumbinary disk with a radius of about 0 3, or 44 au, with a position angle of about 30°, that is misaligned with the orbit of the T Tau S binary. After analyzing the positions and polarization vector patterns of the outflow-related structures, we suggest that T Tau S should trigger the well-known E-W outflow, and is also likely to be responsible for a southwest precessing outflow "coil" and a possible south outflow.

On the Nature of the T Tauri Triple System

“…Additionally, interaction of a wind from T Tau Sa with the circumbinary ring might play an extra role in increasing the diameter of the dynamically cleared ring cavity, as gas and dust are slowly eroded by the wind. High spatial resolution, high contrast near-IR maps of T Tau from Yang et al (2018) revealed evidence for small dust grains that appeared to be streaming toward the west of T Tau S. Particularly, we postulate that the "N3" and "N4" arcs of H-band polarimetric emission identified by Yang et al (2018) could be evidence of small dust grains streaming westward from the circumbinary ring after being eroded by a wide angle wind from T Tau Sa.…”

“…However, a new generation of extremely sensitive high contrast adaptive optics imaging has challenged the outflow geometry found from the past kinematic measurements. Particularly, Herbst et al (2007) and Yang et al (2018) measured high contrast near-IR H 2 and H-band polarized continuum, respectively, and found evidence that T Tau Sa or Sb may be driving a western component of the outflows, previously attributed to T Tau N. As observations of the inner environment of T Tau have improved and become more sensitive, confusion in the orientation and nature of the outflows from the system has followed.…”

“…Although the inner regions of HH 155 and 255 may not be well collimated, structure observed in the innermost knots can provide a record of the kinematics which drive the flows. High spatial resolution adaptive optics imaging investigations of the morphologies in extended emission features within ∼2 of T Tauri have provided some conflicting results on the origins of the inner outflows, with postulation that T Tau S drives the strong western flow (Herbst et al 2007;Yang et al 2018). However, imaging alone does not provide a complete picture; understanding the gas velocities is especially important to identify the sources of outflows.…”

“…Figure 2 demonstrates the strong flux attenuation and solid state absorption features in the SED of T Tau S. Because of the significant obscuration toward the T Tau S binary and small extinction toward T Tau N, the attenuating material that causes the ice and silicate absorption has been best described as a circumbinary disk encircling the T Tau Sa+Sb stars. Indirect evidence for a circumbinary distribution of material encircling T Tau S has been detected in near IR polarimetric maps (Yang et al 2018), and as a dimming at its position in the background ultraviolet (UV) molecular hydrogen emission (Walter et al 2003). However, spatially resolved IR measurements suggest that the flux attenuation of Sb may be significantly less than Sa (Ratzka et al 2009).…”

ALMA Super-resolution Imaging of T Tau: r = 12 au Gap in the Compact Dust Disk around T Tau N

“…The T Tau N disk was found to be a bright disk with a total flux of ∼ 180 mJy at 1.3 mm, but is only seen as a flat compact disk with a radius of ∼ 20 au. Similarly, neither ground-based near-infrared adaptive optics observations nor space-based optical observations can resolve the disk around T Tau N and T Tau Sa/Sb well with a resolution of ∼ 0 .07 or 10 au (e.g., Yang et al 2018). Intriguingly, Manara et al (2019) pointed out that significance residuals (∼ 3σ) were found both at the T Tau N and T Tau S after subtracting axisymmetric models of the two sources from the ALMA continuum image.…”