SEARCHING FOR CIRCUMPLANETARY DISKS AROUND LkCa 15

We present Karl G. Jansky Very Large Array (VLA) observations of the 7 mm continuum emission from the disk surrounding the young star LkCa 15. The observations achieve an angular resolution of 70 mas and spatially resolve the circumstellar emission on a spatial scale of 9 AU. The continuum emission traces a dusty annulus of 45 AU in radius that is consistent with the dust morphology observed at shorter wavelengths. The VLA observations also reveal a compact source at the center of the disk, possibly due to thermal emission from hot dust or ionized gas located within a few AU from the central star. No emission is observed between the star and the dusty ring and, in particular, at the position of the candidate protoplanet LkCa 15 b. By comparing the observations with theoretical models for circumplanetary disk emission, we find that if LkCa 15 b is a massive planet (>5 M_J ) accreting at a rate greater than 10^(–6) M_J yr^(–1), then its circumplanetary disk is less massive than 0.1 M_J , or smaller than 0.4 Hill radii. Similar constraints are derived for any possible circumplanetary disk orbiting within 45 AU from the central star. The mass estimates are uncertain by at least one order of magnitude due to the uncertainties on the mass opacity. Future ALMA observations of this system might be able to detect circumplanetary disks down to a mass of 5 × 10^(–4) M_J and as small as 0.2 AU, providing crucial constraints on the presence of giant planets in the act of forming around this young star.

[1]  Th. Henning,et al.  Large dust particles in disks around T Tauri stars , 2006 .

[2]  M. Ireland,et al.  LkCa 15: A YOUNG EXOPLANET CAUGHT AT FORMATION? , 2011, 1110.3808.

[3]  C. A. Grady,et al.  SPIRAL ARMS IN THE ASYMMETRICALLY ILLUMINATED DISK OF MWC 758 AND CONSTRAINTS ON GIANT PLANETS , 2012, 1212.1466.

[4]  K. Rice,et al.  Protostars and Planets V , 2005 .

[5]  D. Wilner,et al.  A CLOSER LOOK AT THE LkCa 15 PROTOPLANETARY DISK , 2011, 1110.3865.

[6]  J. Pollack,et al.  Composition and radiative properties of grains in molecular clouds and accretion disks , 1994 .

[7]  Jonathan P. Williams,et al.  THE TW Hya DISK AT 870 μm: COMPARISON OF CO AND DUST RADIAL STRUCTURES , 2011, 1111.5037.

[8]  Dynamical Masses of T Tauri Stars and Calibration of Pre-Main-Sequence Evolution , 2000, astro-ph/0008370.

[9]  Local Enhancement of the Surface Density in the Protoplanetary Ring Surrounding HD 142527 , 2013, 1309.7400.

[10]  A. Crida,et al.  ACCRETION OF JUPITER-MASS PLANETS IN THE LIMIT OF VANISHING VISCOSITY , 2013, 1312.6302.

[11]  J. Pety,et al.  Resolving the inner dust disks surrounding LkCa 15 and MWC 480 at mm wavelengths , 2006, astro-ph/0610200.

[12]  W. Rice,et al.  Enhanced dust emission in the HL Tau disc: a low‐mass companion in formation? , 2008, 0809.4151.

[13]  Catherine Espaillat,et al.  TRANSITIONAL AND PRE-TRANSITIONAL DISKS: GAP OPENING BY MULTIPLE PLANETS? , 2010, 1012.4395.

[14]  Catherine Espaillat,et al.  RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS , 2011, 1103.0284.

[15]  J. Carpenter,et al.  ON THE NATURE OF THE TRANSITION DISK AROUND LkCa 15 , 2012, 1201.1001.

[16]  LkHα 330: Evidence for Dust Clearing through Resolved Submillimeter Imaging , 2008 .

[17]  Andrea Isella,et al.  LARGE-SCALE ASYMMETRIES IN THE TRANSITIONAL DISKS OF SAO 206462 AND SR 21 , 2014 .

[18]  Dimitri Mawet,et al.  Flows of gas through a protoplanetary gap , 2013, Nature.

[19]  Gennaro D'Angelo,et al.  Nested-grid calculations of disk-planet interaction , 2001, astro-ph/0112429.

[20]  R. Briguglio,et al.  DISCOVERY OF Hα EMISSION FROM THE CLOSE COMPANION INSIDE THE GAP OF TRANSITIONAL DISK HD 142527 , 2014, 1401.1273.

[21]  G. Anglada,et al.  HIGH ANGULAR RESOLUTION RADIO OBSERVATIONS OF THE HL/XZ TAU REGION: MAPPING THE 50 AU PROTOPLANETARY DISK AROUND HL TAU AND RESOLVING XZ TAU S INTO A 13 AU BINARY , 2009, 0901.3744.

[22]  J. Carpenter,et al.  STRUCTURE AND EVOLUTION OF PRE-MAIN-SEQUENCE CIRCUMSTELLAR DISKS , 2009, 0906.2227.

[23]  E. Kokubo,et al.  DIRECT IMAGING OF FINE STRUCTURES IN GIANT PLANET-FORMING REGIONS OF THE PROTOPLANETARY DISK AROUND AB AURIGAE , 2011, 1102.4408.

[24]  Beth Biller,et al.  A LIKELY CLOSE-IN LOW-MASS STELLAR COMPANION TO THE TRANSITIONAL DISK STAR HD 142527 , 2012, 1206.2654.

[25]  Sean M. Andrews,et al.  MATRYOSHKA HOLES: NESTED EMISSION RINGS IN THE TRANSITIONAL DISK OPH IRS 48 , 2012, 1209.1641.

[26]  Accretion Disks around Young Objects. I. The Detailed Vertical Structure , 1998, astro-ph/9806060.

[27]  Tucson,et al.  A Spitzer View of Protoplanetary Disks in the γ Velorum Cluster , 2008, 0806.2639.

[28]  Adam Burrows,et al.  SPECTRAL AND PHOTOMETRIC DIAGNOSTICS OF GIANT PLANET FORMATION SCENARIOS , 2011, 1108.5172.

[29]  William R. Ward,et al.  Formation of the Galilean Satellites: Conditions of Accretion , 2002 .

[30]  Vincent Geers,et al.  A Major Asymmetric Dust Trap in a Transition Disk , 2013, Science.

[31]  Jonathan P. Williams,et al.  A SPATIALLY RESOLVED INNER HOLE IN THE DISK AROUND GM AURIGAE , 2009, 0903.4455.

[32]  Esther Buenzli,et al.  Small vs. large dust grains in transitional disks: do different cavity sizes indicate a planet? - SAO 206462 (HD 135344B) in polarized light with VLT/NACO , 2013, 1311.4195.

[33]  J. Pollack,et al.  Origin and evolution of the Saturn system , 1984 .

[34]  L. Loinard,et al.  VLBA Determination of the Distance to Nearby Star-forming Regions. I. The Distance to T Tauri with 0.4% Accuracy , 2007, 0708.2081.

[35]  Sean M. Andrews,et al.  PROTOPLANETARY DISK STRUCTURES IN OPHIUCHUS , 2009, 0906.0730.

[36]  L. Hartmann,et al.  Pre-Main-Sequence Evolution in the Taurus-Auriga Molecular Cloud , 1995 .

[37]  A. Boley,et al.  THE EVOLUTION OF CIRCUMPLANETARY DISKS AROUND PLANETS IN WIDE ORBITS: IMPLICATIONS FOR FORMATION THEORY, OBSERVATIONS, AND MOON SYSTEMS , 2013, 1302.3538.

[38]  Katherine Rosenfeld,et al.  AN AZIMUTHAL ASYMMETRY IN THE LkHα 330 DISK , 2013, 1307.5848.

[39]  L. Hartmann,et al.  Accretion and the Evolution of T Tauri Disks , 1998 .

[40]  G. Chauvin,et al.  A companion candidate in the gap of the T Chamaeleontis transitional disk , 2011, 1102.4982.

[41]  L. Testi,et al.  MILLIMETER IMAGING OF MWC 758: PROBING THE DISK STRUCTURE AND KINEMATICS , 2010, 1010.3016.

[42]  C. A. Grady,et al.  DISCOVERY OF SMALL-SCALE SPIRAL STRUCTURES IN THE DISK OF SAO 206462 (HD 135344B): IMPLICATIONS FOR THE PHYSICAL STATE OF THE DISK FROM SPIRAL DENSITY WAVE THEORY , 2012, 1202.6139.

[43]  Saeko S. Hayashi,et al.  Near-Infrared Images of Protoplanetary Disk Surrounding HD 142527 , 2006 .

[44]  J. Carpenter,et al.  INVESTIGATING PLANET FORMATION IN CIRCUMSTELLAR DISKS: CARMA OBSERVATIONS OF RY Tau AND DG Tau , 2010, 1003.4318.

[45]  C. Dominik,et al.  Passive Irradiated Circumstellar Disks with an Inner Hole , 2001, astro-ph/0106470.

[46]  Jonathan P. Williams,et al.  SUBMILLIMETER ARRAY OBSERVATIONS OF THE RX J1633.9-2442 TRANSITION DISK: EVIDENCE FOR MULTIPLE PLANETS IN THE MAKING , 2012, 1204.5722.

[47]  L. Mundy,et al.  RESOLVING THE CIRCUMSTELLAR DISK OF HL TAURI AT MILLIMETER WAVELENGTHS , 2011, 1107.5275.

[48]  Simón Casassus Montero Flows of gas through a protoplanetary gap , 2013 .

[49]  R. Perley,et al.  INTEGRATED POLARIZATION PROPERTIES OF 3C48, 3C138, 3C147, AND 3C286 , 2013, 1302.6662.

[50]  R. Canup,et al.  CIRCUMPLANETARY DISK FORMATION , 2010 .

[51]  B. J. Butler,et al.  THE EXPANDED VERY LARGE ARRAY: A NEW TELESCOPE FOR NEW SCIENCE , 2011, 1106.0532.

[52]  P. Goldreich,et al.  Spectral Energy Distributions of T Tauri Stars with Passive Circumstellar Disks , 1997, astro-ph/9706042.