The 2014 Alma Long Baseline Campaign: First Results From High Angular Resolution Observations Toward The Hl Tau Region

C. L. Brogan (1) , L. M. Pérez (2) , T. R. Hunter (1) , W. R. F. Dent (3, 4) , A. S. Hales (1, 4) , R. E. Hills (5) , S. Corder (1, 4) , E. B. Fomalont (1, 4) , C. Vlahakis (4, 3) , Y. Asaki (6, 7) , D. Barkats (4, 3) , A. Hirota (4, 7) , J. A. Hodge (1) , C. M. V. Impellizzeri (1, 4) , R. Kneissl (4, 3) , E. Liuzzo (8) , R. Lucas (9) , N. Marcelino (8) , S. Matsushita (10) , K. Nakanishi (4, 7) , N. Phillips (4, 3) , A. M. S. Richards (11) , I. Toledo (4) , R. Aladro (3) , D. Broguiere (12) , J. R. Cortes (1, 4) , P. C. Cortes (1, 4) , D. Espada (4, 7) , F. Galarza (4) , D. Garcia- Appadoo (4, 3) , L. Guzman- Ramirez (3) , E. M. Humphreys (13) , T. Jung (14) , S. Kameno (4, 7) , R. A. Laing (13) , S. Leon (4, 3) , G. Marconi (4, 3) , A. Mignano (8) , B. Nikolic (5) , L.-A. Nyman (4, 3) , M. Radiszcz (4) , A. Remijan (1, 4) , J. A. Rodón (3) , T. Sawada (4, 7) , S. Takahashi (4, 7) , R. P. J. Tilanus (15) , B. Vila Vilaro (4, 3) , L. C. Watson (3) , T. Wiklind (4, 3) , E. Akiyama (7) , E. Chapillon (16, 12) , I. de Gregorio- Monsalvo (4, 3) , J. Di Francesco (17) , F. Gueth (12) , A. Kawamura (7) , C.-F. Lee (10) , Q. Nguyen Luong (7) , J. Mangum (1) , V. Pietu (12) , P. Sanhueza (7) , K. Saigo (7) , S. Takakuwa (10) , C. Ubach (1) , T. Van Kempen (15) , A. Wootten (1) , A. Castro- Carrizo (12) , H. Francke (3) , J. Gallardo (4) , J. Garcia (4) , S. Gonzalez (4) , T. Hill (4, 3) , T. Kaminski (3) , Y. Kurono (4, 7) , H.-Y. Liu (10) , C. Lopez (4) , F. Morales (4) , K. Plarre (4) , G. Schieven , L. Testi (13) , L. Videla (4) , E. Villard (4, 3) , P. Andreani (13) , J. E. Hibbard (1) , K. Tatematsu (7)

1 NRAO - National Radio Astronomy Observatory [Charlottesville]
2 NRAO - National Radio Astronomy Observatory [Socorro]
3 ESO - European Southern Observatory [Santiago]
4 JAO - Joint ALMA Observatory
5 Cavendish Laboratory
6 ISAS - Institute of Space and Astronautical Science
7 NAOJ - National Astronomical Observatory of Japan
8 OABO - INAF - Osservatorio Astronomico di Bologna
9 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
10 ASIAA - Academia Sinica Institute of Astronomy and Astrophysics
11 Jodrell Bank Centre for Astrophysics
12 IRAM - Institut de RadioAstronomie Millimétrique
13 ESO - European Southern Observatory
14 KASI - Korea Astronomy and Space Science Institute
15 Leiden Observatory [Leiden]
16 AMOR 2015
17 Herzberg Institute of Astrophysics

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}ȯ 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.

Mots clés: LkHα358; techniques: interferometric; stars: individual: HL Tau; submillimeter: planetary systems; XZ Tau; protoplanetary disks; stars: formation

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

C. L. Brogan, L. M. Pérez, T. R. Hunter, W. R. F. Dent, A. S. Hales, et al.. The 2014 Alma Long Baseline Campaign: First Results From High Angular Resolution Observations Toward The Hl Tau Region. The Astrophysical journal letters, 2015, 808 (1), ⟨10.1088/2041-8205/808/1/L3⟩. ⟨hal-01179310⟩