On the Effects of Self-obscuration in the (Sub)Millimeter Spectral Indices and the Appearance of Protostellar Disks
Por:
Galvan-Madrid, Roberto, Liu, Hauyu Baobab, Izquierdo, Andres F., Miotello, Anna, Zhao, Bo, Carrasco-Gonzalez, Carlos, Lizano, Susana, Rodriguez, Luis F.
Publicada:
20 nov 2018
Resumen:
In this paper we explore the effects of self-obscuration in protostellar
disks with a radially decreasing temperature gradient and a colder
midplane. We are motivated by recent reports of resolved dark lanes
(''hamburgers'') and (sub) millimeter spectral indices
systematically below the ISM value for optically thin dust, alpha(ISM) =
3.7. We explore several model grids, scaling disk mass and varying
inclination angle i and observing frequency nu from the VLA Ka band
(similar to 37 GHz) to ALMA Band 8 (similar to 405 GHz). We also
consider the effects of decreasing the index of the (sub-) millimeter
dust opacity power-law beta from 1.7 to 1. We find that a distribution
of disk masses in the range M-disk = 0.01-2M(circle dot) is needed to
reproduce the observed distribution of spectral indices, and that
assuming a fixed beta = 1.7 gives better results than beta = 1. A wide
distribution of disk masses is also needed to produce some cases with
alpha < 2, as reported for some sources in the literature. Such
extremely low spectral indices arise naturally when the selected
observing frequencies sample the appropriate change in the temperature
structure of the optically thick model disk. Our results show that
protostellar disk masses could often be underestimated by > x10, and are
consistent with recent hydrodynamical simulations. Although we do not
rule out the possibility of some grain growth occurring within the short
protostellar timescales, we conclude that self-obscuration needs to be
taken into account.
Filiaciones:
Galvan-Madrid, Roberto:
UNAM, IRyA, Apdo Postal 72-3 Xangari, Morelia 58089, Michoacan, Mexico
Liu, Hauyu Baobab:
ESO, Karl Schwarzschild Str 2, D-85748 Garching, Germany
Acad Sinica, Inst Astron & Astrophys, POB 23-141, Taipei 106, Taiwan
Izquierdo, Andres F.:
UNAM, IRyA, Apdo Postal 72-3 Xangari, Morelia 58089, Michoacan, Mexico
Univ Antioquia, Inst Fis FCEN, Calle 70 52-21, Medellin, Colombia
Miotello, Anna:
ESO, Karl Schwarzschild Str 2, D-85748 Garching, Germany
Zhao, Bo:
Max Planck Inst Extraterrestr Phys MPE, D-85748 Garching, Germany
Carrasco-Gonzalez, Carlos:
UNAM, IRyA, Apdo Postal 72-3 Xangari, Morelia 58089, Michoacan, Mexico
Lizano, Susana:
UNAM, IRyA, Apdo Postal 72-3 Xangari, Morelia 58089, Michoacan, Mexico
Rodriguez, Luis F.:
UNAM, IRyA, Apdo Postal 72-3 Xangari, Morelia 58089, Michoacan, Mexico
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