The 2014 ALMA Long Baseline Campaign: First Results from High Angular Resolution Observations toward the HL Tau Region

Journal
THE ASTROPHYSICAL JOURNAL LETTERS
Date Issued
2015
Author(s)
ALMA Partnership
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Brogan, C. L.
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Pérez, L. M.
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Hunter, T. R.
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Dent, W. R. F.
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Hales, A. S.
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Hills, R. E.
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Corder, S.
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Fomalont, E. B.
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Vlahakis, C.
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Asaki, Y.
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Barkats, D.
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Hirota, A.
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Hodge, J. A.
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Impellizzeri, C. M. V.
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Kneissl, R.
•
•
Lucas, R.
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Marcelino, N.
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Matsushita, S.
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Nakanishi, K.
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Phillips, N.
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Richards, A. M. S.
•
Toledo, I.
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Aladro, R.
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Broguiere, D.
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Cortes, J. R.
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Cortes, P. C.
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Espada, D.
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Galarza, F.
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Garcia-Appadoo, D.
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Guzman-Ramirez, L.
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Humphreys, E. M.
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Jung, T.
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Kameno, S.
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Laing, R. A.
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Leon, S.
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Marconi, G.
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Mignano, A.
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Nikolic, B.
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Nyman, L. -A.
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Radiszcz, M.
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Remijan, A.
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Rodón, J. A.
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Sawada, T.
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Takahashi, S.
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Tilanus, R. P. J.
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Vila Vilaro, B.
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Watson, L. C.
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Wiklind, T.
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Akiyama, E.
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Chapillon, E.
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de Gregorio-Monsalvo, I.
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Di Francesco, J.
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Gueth, F.
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Kawamura, A.
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Lee, C. -F.
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Nguyen Luong, Q.
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Mangum, J.
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Pietu, V.
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Sanhueza, P.
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Saigo, K.
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Takakuwa, S.
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Ubach, C.
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van Kempen, T.
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Wootten, A.
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Castro-Carrizo, A.
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Francke, H.
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Gallardo, J.
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Garcia, J.
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Gonzalez, S.
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Hill, T.
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Kaminski, T.
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Kurono, Y.
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Liu, H. -Y.
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Lopez, C.
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Morales, F.
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Plarre, K.
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Schieven, G.
•
•
Videla, L.
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Villard, E.
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Andreani, P.
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Hibbard, J. E.
•
Tatematsu, K.
DOI
10.1088/2041-8205/808/1/L3
Description
This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00015.SV . ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013 ), as well as the VizieR catalogue access tool, CDS, Strasbourg, France. This paper also makes use of observations made with the NASA/ESA Hubble Space Telescope , obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA). Facility: ALMA .
Abstract
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.″ 075 (10 AU) to 0.″ 025 (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analog HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46\buildrel{\circ}\over{.} 72+/- 0\buildrel{\circ}\over{.} 05) and position angle (+138\buildrel{\circ}\over{.} 02+/- 0\buildrel{\circ}\over{.} 07). We obtain a high-fidelity image of the 1.0 mm spectral index (α), which ranges from α ̃ 2.0 in the optically thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, and we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km s-1 consistent with Keplerian motion around a ̃1.3 {M}☉ star, although complicated by absorption at low blueshifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkHα358 at 2.9 mm.
Volume
808
Issue
1
Start page
L3
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