Abstract
We present Atacama Large Millimeter Array (ALMA) Band 6 observations at 14−20 au spatial resolution of the disk and CO(2-1) outflow around the Class I protostar DG Tau B in Taurus. The disk is very large, both in dust continuum (Reff, 95% = 174 au) and CO (RCO = 700 au). It shows Keplerian rotation around a 1.1 ± 0.2 M⊙ central star and two dust emission bumps at r = 62 and 135 au. These results confirm that large structured disks can form at an early stage where residual infall is still ongoing. The redshifted CO outflow at high velocity shows a striking hollow cone morphology out to 3000 au with a shear-like velocity structure within the cone walls. These walls coincide with the scattered light cavity, and they appear to be rooted within < 60 au in the disk. We confirm their global average rotation in the same sense as the disk, with a specific angular momentum ≃65 au km s−1. The mass-flux rate of 1.7−2.9 × 10−7 M⊙ yr−1 is 35 ± 10 times that in the atomic jet. We also detect a wider and slower outflow component surrounding this inner conical flow, which also rotates in the same direction as the disk. Our ALMA observations therefore demonstrate that the inner cone walls, and the associated scattered light cavity, do not trace the interface with infalling material, which is shown to be confined to much wider angles (> 70°). The properties of the conical walls are suggestive of the interaction between an episodic inner jet or wind with an outer disk wind, or of a massive disk wind originating from 2 to 5 au. However, further modeling is required to establish their origin. In either case, such massive outflow may significantly affect the disk structure and evolution.
Highlights
Jets and outflows are ubiquitous at all stages of star formation
Zapata et al (2015) studied DG Tau B with the Submillimeter Array (SMA) at 200 angular resolution and they report velocity asymmetries across the receding conical CO outflow interpreted as rotation signatures
In this Letter we present continuum, 12 CO(2-1), 13 CO(2-1), and C18 O(2-1) observations acquired with Atacama Large Millimeter Array (ALMA) of the Excluding DG Tau A where bright nebulosity introduces an unusually high measurement error for its G magnitude (Brown et al 2018)
Summary
Jets and outflows are ubiquitous at all stages of star formation. their exact origin and impact on mass and angular momentum extraction are still fundamental open questions (Frank et al 2014). Mottram et al (2017) show that both CO lobes extend up to at least 6000 (8400 au) with opening angles similar to the infrared scattering nebulae They show the absence of HCO+ emission on source, which is typical for young stars with weak envelopes (van Kempen et al 2009). Zapata et al (2015) studied DG Tau B with the Submillimeter Array (SMA) at 200 angular resolution and they report velocity asymmetries across the receding conical CO outflow interpreted as rotation signatures. They propose that the massive redshifted conical outflow traces entrained material from the rotating parent core.
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