ALMA sub-mm maser and dust distribution of VY Canis Majoris

Aims. Cool, evolved stars have copious, enriched winds. Observations have so far not fully constrained models for the shaping and acceleration of these winds. We need to understand the dynamics better, from the pulsating stellar surface to similar to 10 stellar radii, where radiation pressure on dust is fully effective. Asymmetric nebulae around some red supergiants imply the action of additional forces. Methods. We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec accuracy and to resolve the dusty continuum. Results. The 658, 321, and 325 GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position, coinciding with a compact peak offset to the NW of the brightest continuum emission. The maser shells overlap but avoid each other on scales of up to 10 au. Their distribution is broadly consistent with excitation models but the conditions and kinematics are complicated by wind collisions, clumping, and asymmetries.

[1]  K. Menten,et al.  Hifistars herschel/hifi observations of vy canis majoris : Molecular-line inventory of the envelope around the largest known star , 2013, 1310.2400.

[2]  K. Menten,et al.  AN INTERFEROMETRIC SPECTRAL LINE AND IMAGING SURVEY OF VY CANIS MAJORIS IN THE 345 GHz BAND , 2013, 1309.7360.

[3]  A. Kemball,et al.  Simultaneous VLBA polarimetric observations of the v = {1,2} J = 1-0 and v =1, J = 2-1 SiO maser emission towards VY CMa: Maser morphology and pumping , 2013, 1309.2260.

[4]  B. Aringer,et al.  Exploring wind-driving dust species in cool luminous giants II. Constraints from photometry of M-type AGB stars , 2013, 1302.6572.

[5]  J. Cernicharo,et al.  Non-local radiative transfer in strongly inverted masers , 2013, 1301.0253.

[6]  J. Yates,et al.  Evolved star water maser cloud size determined by star size , 2012, 1207.2583.

[7]  M. Gray.  Maser Sources in Astrophysics , 2012 .

[8]  Peter G. Tuthill,et al.  A close halo of large transparent grains around extreme red giant stars , 2012, Nature.

[9]  P. H. Hauschildt,et al.  Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry , 2012, 1203.5194.

[10]  N. Patel,et al.  ARCSECOND RESOLUTION MAPPING OF SULFUR DIOXIDE EMISSION IN THE CIRCUMSTELLAR ENVELOPE OF VY CANIS MAJORIS , 2011, 1111.7004.

[11]  M. Dubernet,et al.  Rotational excitation of 45 levels of ortho/para-H2O by excited ortho/para-H2 from 5 K to 1500 K: state-to-state, effective, and thermalized rate coefficients , 2011 .

[12]  B. Plez,et al.  Radiative hydrodynamics simulations of red supergiant stars - IV. Gray versus non-gray opacities , 2011, 1109.3619.

[13]  E. Josselin,et al.  The mass-loss rates of red supergiants and the de Jager prescription , 2010, 1010.5369.

[14]  M. Elitzur,et al.  Observational evidence for the shrinking of bright maser spots , 2010, 1010.4419.

[15]  K. Menten,et al.  DISTANCE AND KINEMATICS OF THE RED HYPERGIANT VY CMa: VERY LONG BASELINE ARRAY AND VERY LARGE ARRAY ASTROMETRY , 2011 .

[16]  RATE COEFFICIENTS FOR THE COLLISIONAL EXCITATION OF MOLECULES: ESTIMATES FROM AN ARTIFICIAL NEURAL NETWORK , 2009, 0911.2652.

[17]  S. Sakai,et al.  Distance to VY Canis Majoris with VERA , 2008, 0808.0641.

[18]  M. Wittkowski,et al.  The Mira variable S Orionis: relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs , 2007, 0705.4614.

[19]  M. Gurwell,et al.  658 GHz vibrationally-excited water masers with the Submillimeter Array , 2007, Proceedings of the International Astronomical Union.

[20]  R. Humphreys,et al.  The Three-Dimensional Morphology of VY Canis Majoris. I. The Kinematics of the Ejecta , 2007, astro-ph/0702717.

[21]  N. Patel,et al.  Submillimeter Array Observations of 321 GHz Water Maser Emission in Cepheus A , 2007, Proceedings of the International Astronomical Union.

[22]  S. Kwok,et al.  The Molecular Envelope around the Red Supergiant VY CMa , 2006, astro-ph/0611547.

[23]  Peter Woitke,et al.  Too little radiation pressure on dust in the winds of oxygen-rich AGB stars , 2006, astro-ph/0609392.

[24]  A. de Koter,et al.  Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles - I. Theoretical model – Mass-loss history unravelled in VY CMa , 2006, astro-ph/0606299.

[25]  M. Scholz,et al.  Observable effects of dust formation in dynamic atmospheres of M-type Mira variables , 2006, astro-ph/0601383.

[26]  M. Reid,et al.  Radio Photosphere and Mass-Loss Envelope of VY Canis Majoris , 2005, astro-ph/0502586.

[27]  J. Moran,et al.  Interferometric Observation of the Highly Polarized SiO Maser Emission from the v = 1, J = 5-4 Transition Associated with VY Canis Majoris , 2004, astro-ph/0408298.

[28]  J. Yates,et al.  Qualitative reproduction of stellar H2O maser morphology I. Results at a single stellar phase , 2001 .

[29]  Bipolar outflows in OH/IR stars , 2000, astro-ph/0010602.

[30]  J. Yates,et al.  MERLIN observations of water maser proper motions in VY Canis Majoris , 1998 .

[31]  J. Yates,et al.  NON-LOCAL RADIATIVE TRANSFER FOR MOLECULES : MODELLING POPULATION INVERSIONS IN WATER MASERS , 1997 .

[32]  H. J. Habing,et al.  Circumstellar envelopes and Asymptotic Giant Branch stars , 1996 .

[33]  K. Menten,et al.  Discovery of Strong Vibrationally Excited Water Masers at 658 GHz toward Evolved Stars , 1995 .

[34]  E. Greisen,et al.  The NRAO VLA Sky Survey , 1996 .

[35]  J. Cassinelli,et al.  Massive stars : their lives in the interstellar medium : proceedings of a symposium held as part of the 104th annual meeting of the Astronomical Society of the Pacific, at the University of Wisconsin, Madison, Wisconsin, 23-25 June 1992 , 1993 .

[36]  K. Menten,et al.  321 CHz submillimeter water masers around evolved stars , 1991 .

[37]  G. Melnick,et al.  Excitation of millimeter and submillimeter water masers , 1991 .

[38]  K. Menten,et al.  Submillimeter water masers , 1990 .

[39]  G. H. Bowen,et al.  Dynamical modeling of long-period variable star atmospheres , 1988 .

[40]  L. Hartmann,et al.  Momentum and energy deposition in late-type stellar atmospheres and winds , 1980 .

[41]  W. Welch,et al.  Detection of Water in Interstellar Regions by its Microwave Radiation , 1969, Nature.