A Steeper Than Linear Disk Mass–stellar Mass Scaling Relation

Abstract

The disk mass is among the most important input parameter for every planet formation model to determine the number and masses of the planets that can form. We present an ALMA 887 μm survey of the disk population around objects from ∼2 to 0.03 M e in the nearby ∼2 Myr old ChamaeleonI star-forming region. We detect thermal dust emission from 66 out of 93 disks, spatially resolve 34 of them, and identify two disks with large dust cavities of about 45 au in radius. Assuming isothermal and optically thin emission, we convert the 887 μm flux densities into dust disk masses, hereafter M dust . We find that the -* M M dust relation is steeper than linear and of the form M dust ∝(M * )1.3-1.9 , where the range in the power-law index reflects two extremes of the possible relation between the average dust temperature and stellar luminosity. By reanalyzing all millimeter data available for nearby regions in a self-consistent way, we show that the 1-3 Myr old regions of Taurus, Lupus, and ChamaeleonI share the same -* M M dust relation, while the 10 Myr old UpperSco association has a steeper relation. Theoretical models of grain growth, drift, and fragmentation reproduce this trend and suggest that disks are in the fragmentation-limited regime. In this regime millimeter grains will be located closer in around lower-mass stars, a prediction that can be tested with deeper and higher spatial resolution ALMA observations.

Spiral Arms in Disks: Planets or Gravitational Instability?

“…Sandell et al (2011) performed simple model fitting to the spectral energy distribution (SED) of a sample of Herbig disks and found T dust ∼30-70 K. Andrews et al (2013) pointed out the T dust dependence on the stellar luminosity L å and suggested scaling T dust as L 1 4  . Pascucci et al (2016) suggested that the size of the dust disk should also be taken into consideration when estimating T dust .…”

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

“…Over the past few decades, there have been numerous studies of nearby star-forming regions at millimeter wavelengths with the aim of measuring disk masses for large samples of disks, and this work has been accelerated in recent years by the power of ALMA to quickly survey large numbers of sources (e.g., Beckwith et al 1990;Osterloh & Beckwith 1995;Dutrey et al 1996;Andrews & Williams 2005, 2007Eisner et al 2008Eisner et al , 2016Mann & Williams 2010;Andrews et al 2013;Mann et al 2014;Ansdell et al 2016Ansdell et al , 2017Barenfeld et al 2016;Pascucci et al 2016). These surveys have tended to target the population of Class II protostar disks because they are no longer embedded in an envelope, and so estimates of their disk masses are more straightforward.…”

“…It has also been shown that Class II disk masses are correlated with stellar mass (Andrews et al 2013, Ansdell et al 2016Barenfeld et al 2016;Pascucci et al 2016). As such, when comparing disk mass distributions, we must take care to ensure that our samples have similar stellar host properties; otherwise, our disk mass measurements may be biased.…”

“…Class II disks are the easiest to study because, without a protostellar envelope, the entirety of the submillimeter flux can be attributed to disk emission. In the past decade there has been a large effort, particularly with interferometers like the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the SMA, and now ALMA, toward measuring Class II disk masses (Andrews & Williams 2005, 2007Eisner et al 2008;Mann & Williams 2010;Mann et al 2014;Ansdell et al 2016Ansdell et al , 2017Barenfeld et al 2016;Pascucci et al 2016). These studies typically find that the majority of these disks fall well below the  -M 0.01 0.1 needed to form planetary systems like our own (e.g., Weidenschilling 1977;Desch 2007).…”

An ALMA Survey of DCN/H13CN and DCO+/H13CO+ in Protoplanetary Disks

“…Recent ALMA continuum and CO surveys of disks in various star-forming regions have now created a rich selection of potential chemistry follow-up targets spanning a range of stellar and disk properties (e.g. Ansdell et al 2016;Barenfeld et al 2016;Testi et al 2016;Pascucci et al 2016). …”