2 research outputs found
New Insights into the Nature of Transition Disks from a Complete Disk Survey of the Lupus Star-forming Region
Transition disks with large dust cavities around young stars are promising
targets for studying planet formation. Previous studies have revealed the
presence of gas cavities inside the dust cavities hinting at recently formed,
giant planets. However, many of these studies are biased towards the brightest
disks in the nearby star forming regions, and it is not possible to derive
reliable statistics that can be compared with exoplanet populations. We present
the analysis of 11 transition disks with large cavities (>20 AU radius) from a
complete disk survey of the Lupus star forming region, using ALMA Band 7
observations at 0.3" (22-30 AU radius) resolution of the 345 GHz continuum,
13CO and C18O 3-2 observations and the Spectral Energy Distribution of each
source. Gas and dust surface density profiles are derived using the
physical-chemical modeling code DALI. This is the first study of transition
disks of large cavities within a complete disk survey within a star forming
region. The dust cavity sizes range from 20-90 AU radius and in three cases, a
gas cavity is resolved as well. The deep drops in gas density and large dust
cavity sizes are consistent with clearing by giant planets. The fraction of
transition disks with large cavities in Lupus is ~11%, which is inconsistent
with exoplanet population studies of giant planets at wide orbits. Furthermore,
we present a hypothesis of an evolutionary path for large massive disks
evolving into transition disks with large cavities
ALMA SURVEY of LUPUS PROTOPLANETARY DISKS. I. DUST and GAS MASSES
We present the first high-resolution sub-mm survey of both dust and gas for a
large population of protoplanetary disks. Characterizing fundamental properties
of protoplanetary disks on a statistical level is critical to understanding how
disks evolve into the diverse exoplanet population. We use ALMA to survey 89
protoplanetary disks around stars with in the young
(1--3~Myr), nearby (150--200~pc) Lupus complex. Our observations cover the
890~m continuum and the CO and CO 3--2 lines. We use the
sub-mm continuum to constrain to a few Martian masses
(0.2--0.4~) and the CO isotopologue lines to constrain to roughly a Jupiter mass (assuming ISM-like
abundance). Of 89 sources, we detect 62 in continuum, 36 in CO, and 11
in CO at significance. Stacking individually undetected
sources limits their average dust mass to Lunar masses
(0.03~), indicating rapid evolution once disk clearing begins. We
find a positive correlation between and , and present
the first evidence for a positive correlation between and
, which may explain the dependence of giant planet frequency on host
star mass. The mean dust mass in Lupus is 3 higher than in Upper Sco,
while the dust mass distributions in Lupus and Taurus are statistically
indistinguishable. Most detected disks have
and gas-to-dust ratios , assuming ISM-like abundance;
unless CO is very depleted, the inferred gas depletion indicates that planet
formation is well underway by a few Myr and may explain the unexpected
prevalence of super-Earths in the exoplanet population