Protostellar Disks Research Articles

Fluid Dynamic Aspects of Protostellar Disks Formation

Abstract An analysis is presented of fluid dynamic aspects of the interaction between a disk and the infall of material from a surrounding non-magnetized rotating molecular cloud. The study put emphasis on the accretion shock formed in the vicinity of the disk and the post-shock flow field. This post-shock flow is considered parallel to the disk symmetry plane involving a super-Keplerian azimuthal velocity field v ∼ 1/r (potential vortex). The relative rotation between fluid and the nearly Keplerian rotating thin disk induces along its symmetry plane a boundary layer capable of transporting large quantities of fluid inward. This radial flow results in an axial flow i.e., a mass ejection from the boundary layer with axial jet flow velocities of up to about 300 km s−1.

First Abundance Measurement of Organic Molecules in the Atmosphere of HH 212 Protostellar Disk

Abstract HH 212 is one of the well-studied protostellar systems, showing the first vertically resolved disk with a warm atmosphere around the central protostar. Here we report a detection of nine organic molecules (including newly detected ketene, formic acid, deuterated acetonitrile, methyl formate, and ethanol) in the disk atmosphere, confirming that the disk atmosphere is, for HH 212, the chemically rich component, identified before at a lower resolution as a “hot corino.” More importantly, we report the first systematic survey and abundance measurement of organic molecules in the disk atmosphere within ∼40 au of the central protostar. The relative abundances of these molecules are similar to those in the hot corinos around other protostars and in Comet Lovejoy. These molecules can be either (i) originally formed on icy grains and then desorbed into gas phase or (ii) quickly formed in the gas phase using simpler species ejected from the dust mantles. The abundances and spatial distributions of the molecules provide strong constraints on models of their formation and transport in star formation. These molecules are expected to form even more complex organic molecules needed for life and deeper observations are needed to find them.

Disc formation and fragmentation using radiative non-ideal magnetohydrodynamics

We investigate the formation and fragmentation of discs using a suite of three-dimensional smoothed particle radiative magnetohydrodynamics simulations. Our models are initialised as 1M$_\odot$ rotating Bonnor-Ebert spheres that are threaded with a uniform magnetic field. We examine the effect of including ideal and non-ideal magnetic fields, the orientation and strength of the magnetic field, and the initial rotational rate. We follow the gravitational collapse and early evolution of each system until the final classification of the protostellar disc can be determined. Of our 105 models, 41 fragment, 21 form a spiral structure but do not fragment, and another 12 form smooth discs. Fragmentation is more likely to occur for faster initial rotation rates and weaker magnetic fields. For stronger magnetic field strengths, the inclusion of non-ideal MHD promotes disc formation, and several of these models fragment, whereas their ideal MHD counterparts do not. For the models that fragment, there is no correlation between our parameters and where or when the fragmentation occurs. Bipolar outflows are launched in only 17 models, and these models have strong magnetic fields that are initially parallel to the rotation axis. Counter-rotating envelopes form in four slowly-rotating, strong-field models -- including one ideal MHD model -- indicating they form only in a small fraction of the parameter space investigated.

Star-forming regions at the periphery of the supershell surrounding the Cyg OB1 association - II. ISM kinematics and YSOs in the star cluster vdB 130 region

ABSTRACT We present an observational study of small-scale feedback processes operating in the star-forming region located in the wall of the expanding supershell around the Cyg OB1 association. The interstellar gas and dust content and pre-stellar populations in the vicinity of the open star cluster vdB 130 are analysed based on new optical and IR observations performed with the 6-m (3D spectroscopic mapping in the [S ii] doublet) and 2.5-m (optical and NIR images) Russian telescopes along with the archival data of Spitzer and Herschel space telescopes. Analysing ionized gas kinematics and emission spectra, we discovered a compact region with supersonic motions. These motions may be caused either by stellar wind or a bipolar outflow from a protostellar disc. Young stellar objects were identified and classified in the area under study. Two star-forming regions were identified. One of them is a region of ongoing star formation in the head of the molecular cloud observed there and another one is a burst of star formation in the cloud tail.

The role of initial magnetic field structure in the launching of protostellar jets

Magnetic fields are known to play a crucial role in the star formation process, particularly in the formation of jets and outflows from protostellar discs. The magnetic field structure in star forming regions is not always uniform and ordered, often containing regions of magnetic turbulence. We present grid-based, magneto-hydrodynamical simulations of the collapse of a 1$\,\mathrm{M}_{\odot}$ cloud core, to investigate the influence of complex magnetic field structures on outflow formation, morphology and efficiency. We compare three cases: a uniform field, a partially turbulent field and a fully turbulent field, with the same magnetic energy in all three cases. We find that collimated jets are produced in the uniform-field case, driven by a magneto-centrifugal mechanism. Outflows also form in the partially turbulent case, although weaker and less collimated, with an asymmetric morphology. The outflows launched from the partially turbulent case carry the same amount of mass as the uniform-field case but at lower speeds, having only have 71$\%$ of the momentum of the uniform-field case. In the case of a fully turbulent field, we find no significant outflows at all. Moreover, the turbulent magnetic field initially reduces the accretion rate and later induces fragmentation of the disc, forming multiple protostars. We conclude that a uniform poloidal component of the magnetic field is necessary for the driving of jets.

Time Evolution of 3D Disk Formation with Misaligned Magnetic Field and Rotation Axes

Abstract Distinguishing diagnostic observational signatures produced by MHD models is essential in understanding the physics for the formation of protostellar disks in the Atacama Large Millimeter/submillimeter Array era. Developing suitable tools along with time evolution will facilitate better identification of diagnostic features. With the ray-tracing-based radiative transfer code Perspective we explore the time evolution of MHD models carried out in Li et al.—most of which have 90° misalignment between the rotational axis and the magnetic field. Four visible object types can be characterized, origins of which are dependent on the initial conditions. Our results show complex spiraling density, velocity, and polarization structures. The systems are under constant change, but many of those distinctive features are present already early on, and they grow more visible in time, but most could not be identified from the data without examining their change in time. The results suggest that spiraling pseudo-disk structures could function as an effective observation signature of the formation process, and we witness accretion in the disk with eccentric orbits that appear as spiral-like perturbation from simple circular Keplerian orbits. Magnetically aligned polarization appears purely azimuthal in the disk, and the magnetic field can lead to precession of the disk.

Unveiling a cluster of protostellar disks around the massive protostar GGD 27 MM1

Context. Most stars form in clusters and thus it is important to characterize the protostellar disk population in dense environments to assess whether the environment plays a role in the subsequent evolution. Specifically, it is critical to evaluate whether planet formation is altered with respect to more isolated stars formed in dark clouds. Aims. We seek to investigate the properties of the protostellar disks in the GGD 27 cluster and compare these with those obtained from disks formed in nearby regions. Methods. We used ALMA to observe the star-forming region GGD 27 at 1.14 mm with an unprecedented angular resolution, 40 mas (∼56 au), and sensitivity (∼0.002 M⊙). Results. We detected a cluster of 25 continuum sources, most of which likely trace disks around Class 0/I protostars. Excluding the two most massive objects, disks masses are in the range 0.003–0.05 M⊙. The analysis of the cluster properties indicates that GGD 27 displays moderate subclustering. This result, combined with the dynamical timescale of the radio jet (∼104 years), suggests the youthfulness of the cluster. The lack of disk mass segregation signatures may support this as well. We found a clear paucity of disks with Rdisk > 100 au. The median value of the radius is 34 au; this value is smaller than the median of 92 au for Taurus but comparable to the value found in Ophiuchus and in the Orion Nebula Cluster. In GGD 27 there is no evidence of a distance-dependent disk mass distribution (i.e., disk mass depletion due to external photoevaporation), most likely due to the cluster youth. There is a clear deficit of disks for distances <0.02 pc. Stars can only form larger and more massive disksfor distances >0.04 pc. This suggests that dynamical interactions far from the cluster center are weaker, although the small disks found could be the result of disk truncation. This work demonstrates the potential to characterize disks from low-mass young stellar objects in distant and massive (still deeply embedded) clustered environments.

Blobs, spiral arms, and a possible planet around HD 169142

Context. Young planets are expected to cause cavities, spirals, and kinematic perturbations in protostellar disks that may be used to infer their presence. However, a clear detection of still-forming planets embedded within gas-rich disks is still rare. Aims. HD 169142 is a very young Herbig Ae-Be star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects around this star have been made previously, follow-up studies remain inconclusive. The complex structure of this disk is not yet well understood. Methods. We used the high contrast imager SPHERE at ESO Very large Telescope to obtain a sequence of high-resolution, high-contrast images of the immediate surroundings of this star over about three years in the wavelength range 0.95–2.25 μm. This enables a photometric and astrometric analysis of the structures in the disk. Results. While we were unable to definitively confirm the previous claims of a massive sub-stellar object at 0.1–0.15 arcsec from the star, we found both spirals and blobs within the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star. While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings, along the primary arm of the spiral design. Conclusions. This blob might be due to a planet that might also be responsible for the spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected at short wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might be responsible for the emission observed in the K1 and K2 bands. The mass ofthis putative planet may be constrained using photometric and dynamical arguments. While uncertainties are large, the mass should be between 1 and 4 Jupiter masses. The brightest blobs are found at the 1:2 resonance with this putative planet.

Pebble accretion in self-gravitating protostellar discs

Abstract Pebble accretion has become a popular component to core accretion models of planet formation, and is especially relevant to the formation of compact, resonant terrestrial planetary systems. Pebbles initially form in the inner protoplanetary disc, sweeping outwards in a radially expanding front, potentially forming planetesimals and planetary cores via migration and the streaming instability. This pebble front appears at early times, in what is typically assumed to be a low-mass disc. We argue this picture is in conflict with the reality of young circumstellar discs, which are massive and self-gravitating. We apply standard pebble accretion and streaming instability formulae to self-gravitating protostellar disc models. Fragments will open a gap in the pebble disc, but they will likely fail to open a gap in the gas, and continue rapid inward migration. If this does not strongly perturb the pebble disc, our results show that disc fragments will accrete pebbles efficiently. We find that in general the pebble-to-gas-density ratio fails to exceed 0.01, suggesting that the streaming instability will struggle to operate. It may be possible to activate the instability if 10 cm grains are available, and spiral structures can effectively concentrate them in regions of low gravito-turbulence. If this occurs, lunar mass cores might be assembled on time-scales of a few thousand years, but this is likely to be rare, and is far from proven. In any case, this work highlights the need for study of how self-gravitating protostellar discs define the distribution and properties of solid bodies, for future planet formation by core accretion.

Orion SrcI’s Disk Is Salty

Abstract We report the detection of NaCl, KCl, and their 37Cl and 41K isotopologues toward the disk around Orion SrcI. About 60 transitions of these molecules were identified. This is the first detection of these molecules in the interstellar medium not associated with the ejecta of evolved stars. It is also the first ever detection of the vibrationally excited states of these lines in the ISM above v = 1, with firm detections up to v = 6. The salt emission traces the region just above the continuum disk, possibly forming the base of the outflow. The emission from the vibrationally excited transitions is inconsistent with a single temperature, implying the lines are not in LTE. We examine several possible explanations of the observed high excitation lines, concluding that the vibrational states are most likely to be radiatively excited via rovibrational transitions in the 25–35 (NaCl) and 35–45 (KCl) range. We suggest that the molecules are produced by destruction of dust particles. Because these molecules are so rare, they are potentially unique tools for identifying high-mass protostellar disks and measuring the radiation environment around accreting young stars.

Near-equilibrium isotope fractionation during planetesimal evaporation

Silicon and Mg in differentiated rocky bodies exhibit heavy isotope enrichments that have been attributed to evaporation of partially or entirely molten planetesimals. We evaluate the mechanisms of planetesimal evaporation in the early solar system and the conditions that controlled attendant isotope fractionations.Energy balance at the surface of a body accreted within ~1 Myr of CAI formation and heated from within by 26Al decay results in internal temperatures exceeding the silicate solidus, producing a transient magma ocean with a thin surface boundary layer of order <1 m that would be subject to foundering. Bodies that are massive enough to form magma oceans by radioisotope decay (≥0.1% M⊕) can retain hot rock vapor even in the absence of ambient nebular gas. We find that a steady-state rock vapor forms within minutes to hours and results from a balance between rates of magma evaporation and atmospheric escape. Vapor pressure buildup adjacent to the surfaces of the evaporating magmas would have inevitably led to an approach to equilibrium isotope partitioning between the vapor phase and the silicate melt. Numerical simulations of this near-equilibrium evaporation process for a body with a radius of ~700 km yield a steady-state far-field vapor pressure of 10−8 bar and a vapor pressure at the surface of 10−4 bar, corresponding to 95% saturation. Approaches to equilibrium isotope fractionation between vapor and melt should have been the norm during planet formation due to the formation of steady-state rock vapor atmospheres and/or the presence of protostellar gas.We model the Si and Mg isotopic composition of bulk Earth as a consequence of accretion of planetesimals that evaporated subject to the conditions described above. The results show that the best fit to bulk Earth is for a carbonaceous chondrite-like source material with about 12% loss of Mg and 15% loss of Si resulting from near-equilibrium evaporation into the solar protostellar disk of H2 on timescales of 104 to 105 years.

Characterizing young protostellar disks with the CALYPSO IRAM-PdBI survey: large Class 0 disks are rare

Context.Understanding the formation mechanisms of protoplanetary disks and multiple systems and also their pristine properties are key questions for modern astrophysics. The properties of the youngest disks, embedded in rotating infalling protostellar envelopes, have largely remained unconstrained up to now.Aims.We aim to observe the youngest protostars with a spatial resolution that is high enough to resolve and characterize the progenitors of protoplanetary disks. This can only be achieved using submillimeter and millimeter interferometric facilities. In the framework of the IRAM Plateau de Bure Interferometer survey CALYPSO, we have obtained subarcsecond observations of the dust continuum emission at 231 and 94 GHz for a sample of 16 solar-type Class 0 protostars.Methods.In an attempt to identify disk-like structures embedded at small scales in the protostellar envelopes, we modeled the dust continuum emission visibility profiles using Plummer-like envelope models and envelope models that include additional Gaussian disk-like components.Results.Our analysis shows that in the CALYPSO sample, 11 of the 16 Class 0 protostars are better reproduced by models including a disk-like dust continuum component contributing to the flux at small scales, but less than 25% of these candidate protostellar disks are resolved at radii &gt;60 au. Including all available literature constraints on Class 0 disks at subarcsecond scales, we show that our results are representative: most (&gt;72% in a sample of 26 protostars) Class 0 protostellar disks are small and emerge only at radii &lt;60 au. We find a multiplicity fraction of the CALYPSO protostars ≲57% ± 10% at the scales 100–5000 au, which generally agrees with the multiplicity properties of Class I protostars at similar scales.Conclusions.We compare our observational constraints on the disk size distribution in Class 0 protostars to the typical disk properties from protostellar formation models. If Class 0 protostars contain similar rotational energy as is currently estimated for prestellar cores, then hydrodynamical models of protostellar collapse systematically predict a high occurrence of large disks. Our observations suggest that these are rarely observed, however. Because they reduce the centrifugal radius and produce a disk size distribution that peaks at radii &lt;100 au during the main accretion phase, magnetized models of rotating protostellar collapse are favored by our observations.

The Role of Magnetic Fields in the Formation of Protostellar Discs

Truncated abstract: The formation of a protostellar disc is a natural outcome during the star formation process. As gas in a molecular cloud core collapses under self-gravity, the angular momentum of the gas will slow its collapse on small scales and promote the formation of a protostellar disc. Although the angular momenta of dense star-forming cores remain to be fully characterized observationally, existing data indicates that typical cores have enough angular momenta to form relatively large, rotationally supported discs. However, molecular clouds are observed to be permeated by magnetic fields, which can strongly affect the evolution of angular momentum through magnetic braking. Indeed, in the ideal MHD limit, magnetic braking has been shown to be so efficient as to remove essentially all of the angular momentum of the material close to the forming star such that disc formation is suppressed. This is known as the magnetic braking catastrophe. The catastrophe must be averted in order for the all-important rotationally supported discs to appear, but when and how this happens remains debated. We review the resolutions proposed to date, with emphasis on misalignment, turbulence and especially non-ideal effects. The dissipative non-ideal effects weaken the magnetic field, and the dispersive term redirects it to promote or hinder disc formation. When self-consistently applying non-ideal processes, rotationally supported discs of at least tens of au form, thus preventing the magnetic braking catastrophe. The non-ideal processes are sensitive to the magnetic field strength, cosmic ray ionization rate, and gas and dust grain properties, thus a complete understanding of the host molecular cloud is required. Therefore, the properties of the host molecular cloud -- and especially its magnetic field -- cannot be ignored when numerically modelling the formation and evolution of protostellar discs.

ALMA detects a radial disk wind in DG Tauri

Aims. We aim to use the high spatial resolution of the Atacama Large Millimeter/submillimeter Array (ALMA) to map the flow pattern of molecular gas near DG Tauri and its disk, a young stellar object driving a jet and a molecular outflow. Methods. We use observations from ALMA in the J = 2 − 1 transition of 12CO, 13CO, and C18O to study the Keplerian disk of DG Tauri and outflows that may be related to the disk and the jet. Results. We find a new wind component flowing radially at a steep angle (≈25° from the vertical) above the disk with a velocity of ≈3.1 km s−1. It continues the trend of decreasing velocity for increasing distance from the jet axis (“onion-like velocity structure”). Conclusions. The new component is located close to the protostellar disk surface and may be related to photoevaporative winds.

On the Effects of Self-obscuration in the (Sub)Millimeter Spectral Indices and the Appearance of Protostellar Disks

Abstract 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, α ISM = 3.7. We explore several model grids, scaling disk mass and varying inclination angle i and observing frequency ν from the VLA Ka band (∼37 GHz) to ALMA Band 8 (∼405 GHz). We also consider the effects of decreasing the index of the (sub-)millimeter dust opacity power-law β from 1.7 to 1. We find that a distribution of disk masses in the range M disk = 0.01–2 M ⊙ is needed to reproduce the observed distribution of spectral indices, and that assuming a fixed β = 1.7 gives better results than β = 1. A wide distribution of disk masses is also needed to produce some cases with α &lt; 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 &gt; ×10, 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.

The interplay between the viscosity and EUV radiation on the dispersal of protoplanetary discs

A key issue in the evolution of protostellar discs is the analysis of the mechanisms by which the disc is eventually dispersed and the time-scales involved in this process. The photoevaporation is very likely an important process in dispersing discs material and for explaining the observational time-scales needed for reaching a discless status. We analyze the role of the EUV radiation on a variety of disc models when different viscosity values are used. Our analysis focus on the changes of different diagnostic indicators commonly used for comparison of discs models and observed systems.

An Ultra Metal-poor Star Near the Hydrogen-burning Limit*

Abstract It is unknown whether or not low-mass stars can form at low metallicity. While theoretical simulations of Population III (Pop III) star formation show that protostellar disks can fragment, it is impossible for those simulations to discern if those fragments survive as low-mass stars. We report the discovery of a low-mass star on a circular orbit with orbital period P = 34.757 ± 0.010 days in the ultra metal-poor (UMP) single-lined spectroscopic binary system 2MASS J18082002–5104378. The secondary star 2MASS J18082002–5104378 B has a mass M 2 = 0.14 − 0.01 + 0.06 M ⊙ , placing it near the hydrogen-burning limit for its composition. The 2MASS J18082002–5104378 system is on a thin disk orbit as well, making it the most metal-poor thin disk star system by a considerable margin. The discovery of 2MASS J18082002–5104378 B confirms the existence of low-mass UMP stars and its short orbital period shows that fragmentation in metal-poor protostellar disks can lead to the formation and survival of low-mass stars. We use scaling relations for the typical fragment mass and migration time along with published models of protostellar disks around both UMP and primordial composition stars to explore the formation of low-mass Pop III stars via disk fragmentation. We find evidence that the survival of low-mass secondaries around solar-mass UMP primaries implies the survival of solar-mass secondaries around Pop III primaries with masses 10 M ⊙ ≲ M * ≲ 100 M ⊙ . If true, this inference suggests that solar-mass Pop III stars formed via disk fragmentation could survive to the present day.

The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). V. 18 Candidate Disks around Class 0 and I Protostars in the Perseus Molecular Cloud

Abstract We present the full disk-fit results VANDAM survey of all Class 0 and I protostars in the Perseus molecular cloud. We have 18 new protostellar disk candidates around Class 0 and I sources, which are well described by a simple, parametrized disk model fit to the 8 mm VLA dust continuum observations. 33% of Class 0 protostars and just 11% of Class I protostars have candidate disks, while 78% of Class 0 and I protostars do not have signs of disks within our 12 au disk diameter resolution limit, indicating that at 8 mm most disks in the Class 0 and I phases are &lt;10 au in radius. These small radii may be a result of surface brightness sensitivity limits. Modeled 8 mm radii are similar to the radii of known Class 0 disks with detected Keplerian rotation. Since our 8 mm data trace a population of larger dust grains that radially drift toward the protostar and are lower limits on true disk sizes, large disks at early times do not seem to be particularly rare. We find statistical evidence that Class 0 and I disks are likely drawn from the same distribution, meaning disk properties may be defined early in the Class 0 phase and do not undergo large changes through the Class I phase. By combining our candidate disk properties with previous polarization observations, we find a qualitative indication that misalignment between inferred envelope-scale magnetic fields and outflows may indicate disks on smaller scales in Class 0 sources.

Gravitational fragmentation and formation of giant protoplanets on orbits of tens of au

Aims. Migration of dense gaseous clumps that form in young protostellar disks via gravitational fragmentation is investigated to determine the likelihood of giant planet formation. Methods. High-resolution numerical hydrodynamics simulations in the thin-disk limit are employed to compute the formation and long-term evolution of a gravitationally unstable protostellar disk around a solar-mass star. Results. We show that gaseous clumps that form in the outer regions of the disk (&gt;100 au) through disk fragmentation are often perturbed by other clumps or disk structures, such as spiral arms, and migrate toward the central star on timescales from a few thousand to few tens of thousands of years. The migration timescale is slowest when stellar motion in response to the disk gravity is considered. When approaching the star, the clumps first gain mass (up to several tens of MJup), but then quickly lose most of their diffuse envelopes through tidal torques. Part of the clump envelope can be accreted onto the central star causing an FU-Orionis-type accretion and luminosity outburst. The tidal mass loss helps the clumps to significantly slow down or even halt their inward migration at a distance of a few tens of au from the protostar. The resulting clumps are heavily truncated both in mass and size compared to their wider orbit counterparts, keeping only a dense and hot nucleus. During the inward migration, the temperature in the clump interiors may exceed the molecular hydrogen dissociation limit (2000 K) and the central region of the clump can collapse into a gas giant protoplanet. Moreover, migrating clumps may experience close encounters with other clumps, resulting in the ejection of the least massive (planetary-mass) clumps from the disk. We argue that FU-Orionis-type luminosity outbursts may be the end product of disk fragmentation and clump inward migration, preceding the formation of giant protoplanets on tens of au orbits in systems such as HR 8799.

The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). IV. Free–Free Emission from Protostars: Links to Infrared Properties, Outflow Tracers, and Protostellar Disk Masses

Abstract Emission from protostars at centimeter radio wavelengths has been shown to trace the free–free emission arising from ionizing shocks as a result of jets and outflows driven by protostars. Therefore, measuring properties of protostars at radio frequencies can provide valuable insights into the nature of their outflows and jets. We present a C-band (4.1 and 6.4 cm) survey of all known protostars (Class 0 and Class I) in Perseus as part of the VLA Nascent Disk and Multiplicity (VANDAM) Survey. We examine the known correlations between radio flux density and protostellar parameters, such as bolometric luminosity and outflow force, for our sample. We also investigate the relationship between radio flux density and far-infrared line luminosities from Herschel. We show that free–free emission most likely originates from J-type shocks; however, the large scatter indicates that those two types of emission probe different time and spatial scales. Using C-band fluxes, we removed an estimation of free–free contamination from the corresponding Ka-band (9 mm) flux densities that primarily probe dust emission from embedded disks. We find that the compact (&lt;1″) dust emission is lower for Class I sources (median dust mass 96 M ⊕) relative to Class 0 (248 M ⊕), but several times higher than in Class II (5–15 M ⊕). If this compact dust emission is tracing primarily the embedded disk, as is likely for many sources, this result provides evidence of decreasing disk masses with protostellar evolution, with sufficient mass for forming giant planet cores primarily at early times.