arXiv subjects

Marco Tazzari

Publications and source records attributed to Marco Tazzari.

At least 19 recordsLinked to original sources

arXiv2025

Multi-frequency analysis of the ALMA and VLA high resolution continuum observations of the substructured disc around CI Tau. Preference for sub-mm-sized low-porosity amorphous carbon grains

(Abridged) We present high angular resolution and sensitivity ALMA 3.1 mm and VLA 9.1 mm observations of the disc around CI Tau. These new data were combined with similar-resolution archival ALMA 0.9 and 1.3 mm observations and new and archival VLA 7.1 mm, 2.0, 3.0, and 6.0 cm photometry to study the properties of dust in this system. At wavelengths <3.1 mm, CI Tau's continuum emission is very extended and highly substructured (with three gaps, four rings, and two additional gap-ring pairs identified by non-parametric visibility modelling). Instead, the VLA 9.1 mm data are dominated by a bright central component, only partially (< 50%) due to dust emission, surrounded by a marginally detected, faint, and smooth halo. We fitted the ALMA and VLA 9.1 mm data together, adopting a physical model that accounts for the effects of dust absorption and scattering. For our fiducial dust composition ("Ricci" opacities), we retrieved a flat maximum grain size distribution across the disc radius of $(7.1\pm0.8)\times10^{-2}$ cm, that we tentatively attributed to fragmentation of fragile dust or bouncing. We tested, for the first time, the dependence of our results on the adopted dust composition model to assess which mixture can best reproduce the observations. We found that the "Ricci" opacities work better than the traditionally adopted "DSHARP" ones, while graphite-rich mixtures perform significantly worse. We also show that, for our fiducial composition, the data prefer low-porosity (< 70%) grains, in contrast with claims of highly porous aggregates in younger sources, which we tentatively justified by time-dependent compaction. Our results are in line with constraints from disc population synthesis models and naturally arise from CI Tau's peculiar spectral behaviour, making this disc an ideal target for deeper cm-wavelength and dust polarisation follow-ups.

astro-ph.EP↗

arXiv2025

The centimeter emission from planet-forming disks in Taurus

The last decade has witnessed remarkable advances in the characterization of the (sub-)millimeter emission from planet-forming disks. Instead, the study of the (sub-)centimeter emission has made more limited progress, to the point that only a few exceptional disk-bearing objects have been characterized in the centimeter regime. This work takes a broad view of the centimeter emission from a large sample with VLA observations that is selected from previous ALMA surveys of more representative disks in brightness and extent. We report on the detection and characterization of flux at centimeter wavelengths from 21 sources in the Taurus star-forming region. Complemented by literature and archival data, the entire photometry from 0.85 mm to 6 cm is fitted by a two-component model that determines the ubiquitous presence of free-free emission entangled with the dust emission. The flux density of the free-free emission is found to scale with the accretion rate but is independent of the outer disk morphology depicted by ALMA. The dust emission at 2 cm is still appreciable, and offers the possibility to extract an unprecedented large set of dust spectral indices in the centimeter regime. A pronounced change between the median millimeter indices (2.3) and centimeter indices (2.8) suggests that a large portion of the disk emission is optically thick up to 3 mm. The comparison of both indices and fluxes with the ALMA disk extent indicates that this portion can be as large as 40 au, and suggests that the grain population within this disk region that emits the observed centimeter emission is similar in disks with different size and morphology. All these results await confirmation and dedicated dust modeling once facilities like ngVLA or SKA-mid are able to resolve the centimeter emission from planet-forming disks and disentangle the various components.

astro-ph.EP↗

arXiv2024

The evolution of the $M_{\mathrm{d}}-M_{\star}$ and $\dot M-M_{\star}$ correlations traces protoplanetary disc dispersal

(Abridged) Observational surveys of entire star-forming regions have provided evidence of power-law correlations between the disc properties and the stellar mass, especially the disc mass (${M_d \propto M_*}^{\lambda_m}$) and the accretion rate ($\dot M \propto {M_*}^{\lambda_{acc}}$). Whether the secular disc evolution affects said correlations is still debated: while the purely viscous scenario has been probed, other mechanisms could impact differently. We study the evolution of the slopes $\lambda_m$ and $\lambda_{acc}$ in the wind-driven and hybrid case and compare it to the viscous prediction, using a combination of analytical calculations and numerical simulations (performed with the 1D population synthesis code Diskpop, that we also present and release). Assuming $M_d(0) \propto {M_*}^{\lambda_{m, 0}}$ and $\dot M(0) \propto {M_*}^{\lambda_{acc, 0}}$ as initial conditions, we find that viscous and hybrid accretion preserve the shape of the correlations and evolve their slope; on the other hand, MHD winds change the shape of the correlations, bending them according to the scaling of the accretion timescale with the stellar mass. We also show how a spread in the initial conditions conceals this behaviour. We then analyse the impact of disc dispersal, and find that the currently available sample sizes ($\sim 30$ discs at 5 Myr) introduce stochastic oscillations in the slopes evolution, which dominate over the physical signatures. Increasing the sample size could mitigate this issue: $\sim 140$ discs at 5 Myr, corresponding to the complete Upper Sco sample, would give small enough error bars to use the evolution of the slopes as a proxy for the driving mechanism of disc evolution. Finally, we discuss how the observational claim of steepening slopes necessarily leads to an initially steeper $M_d - M_*$ correlation with respect to $\dot M - M_*$.

astro-ph.EP↗

arXiv2023

Dual-Band Observations of the Asymmetric Ring around CIDA 9A: Dead or Alive?

While the most exciting explanation of the observed dust asymmetries in protoplanetary disks is the presence of protoplanets, other mechanisms can also form the dust features. This paper presents dual-wavelength Atacama Large Millimeter/submillimeter Array (ALMA) observations of a large asymmetric dusty ring around the M-type star CIDA 9A. We detect a dust asymmetry in both 1.3 mm and 3.1 mm data. To characterize the asymmetric structure, a parametric model is used to fit the observed visibilities. We report a tentative azimuthal shift of the dust emission peaks between the observations at the two wavelengths. This shift is consistent with a dust trap caused by a vortex, which may be formed by an embedded protoplanet or other hydrodynamical instabilities, such as a dead zone. Deep high-spatial observations of dust and molecular gas are needed to constrain the mechanisms that formed the observed millimeter cavity and dust asymmetry in the protoplanetary disk around CIDA 9A.

astro-ph.SR↗

arXiv2023

The time evolution of $M_{\mathrm{d}}/\dot M$ in protoplanetary discs as a way to disentangle between viscosity and MHD winds

As the classic viscous paradigm for protoplanetary disk accretion is challenged by the observational evidence of low turbulence, the alternative scenario of MHD disk winds is being explored as potentially able to reproduce the same observed features traditionally explained with viscosity. Although the two models lead to different disk properties, none of them has been ruled out by observations - mainly due to instrumental limitations. In this work, we present a viable method to distinguish between the viscous and MHD framework based on the different evolution of the distribution in the disk mass ($M_{\mathrm{d}}$) - accretion rate ($\dot M$) plane of a disk population. With a synergy of analytical calculations and 1D numerical simulations, performed with the population synthesis code \texttt{Diskpop}, we find that both mechanisms predict the spread of the observed ratio $M_{\mathrm{d}}/\dot M$ in a disk population to decrease over time; however, this effect is much less pronounced in MHD-dominated populations as compared to purely viscous populations. Furthermore, we demonstrate that this difference is detectable with the current observational facilities: we show that convolving the intrinsic spread with the observational uncertainties does not affect our result, as the observed spread in the MHD case remains significantly larger than in the viscous scenario. While the most recent data available show a better agreement with the wind model, ongoing and future efforts to obtain direct gas mass measurements with ALMA and ngVLA will cause a reassessment of this comparison in the near future.

astro-ph.EP↗

arXiv2023

Radio multiwavelength analysis of the compact disk CX Tau: Presence of strong free-free variability or anomalous microwave emission

Protoplanetary disks emit radiation across a broad range of wavelengths, requiring a multiwavelength approach to fully understand their physical mechanisms and how they form planets. Observations at sub-millimeter to centimeter wavelengths can provide insights into the thermal emission from dust, free-free emission from ionized gas, and possible gyro-synchrotron emission from the stellar magnetosphere. This work is focused on CX Tau, a ${\sim}0.4\,M_\odot$ star with an extended gas emission and a compact and apparently structureless dust disk, with an average millimeter flux when compared to Class II sources in Taurus. We present observations from the Karl G. Jansky Very Large Array (VLA) across four bands (between 9.0 mm and 6.0 cm) and combine them with archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), the Submillimeter Array (SMA) and the Plateau de Bure Interferometer (PdBI). This multiwavelength approach allows us to separate the dust continuum from other emissions. After isolating the dust thermal emission, we derived an upper limit of the dust disk extent at 1.3 cm which is consistent with theoretical predictions of a radial drift-dominated disk. Centimeter data show a peculiar behavior: deep observations at 6.0 cm did not detect the source, while at 1.3 cm the flux density is anomalously higher than adjacent bands. Intraband spectral indices suggest a dominant contribution from free-free emission, whereas gyro-synchrotron emission is excluded. To explain these observations, we propose a strong variability among the free-free emission with timescales shorter than a month. Another possible interpretation is the presence of anomalous microwave emission from spinning dust grains.

astro-ph.EP↗

arXiv2023

A Large Double-ring Disk around the Taurus M Dwarf J04124068+2438157

Planet formation imprints signatures on the physical structures of disks. In this paper, we present high-resolution ($\sim$50 mas, 8 au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and CO line emission toward the disk around the M3.5 star 2MASS J04124068+2438157. The dust disk consists only of two narrow rings at radial distances of 0.47 and 0.78 arcsec ($\sim$70 and 116 au), with Gaussian $σ$ widths of 5.6 and 8.5 au, respectively. The width of the outer ring is smaller than the estimated pressure scale height by $\sim25\%$, suggesting dust trapping in a radial pressure bump. The dust disk size, set by the location of the outermost ring, is significantly larger (by $3σ$) than other disks with similar millimeter luminosity, which can be explained by an early formation of local pressure bump to stop radial drift of millimeter dust grains. After considering the disk's physical structure and accretion properties, we prefer planet--disk interaction over dead zone or photoevaporation models to explain the observed dust disk morphology. We carry out high-contrast imaging at $L'$ band using Keck/NIRC2 to search for potential young planets, but do not identify any source above $5σ$. Within the dust gap between the two rings, we reach a contrast level of $\sim$7 mag, constraining the possible planet below $\sim$2--4 $M_{\rm Jup}$. Analyses of the gap/ring properties suggest a $\sim$Saturn mass planet at $\sim$90 au is likely responsible for the formation of the outer ring, which can be potentially revealed with JWST.

astro-ph.EP↗

arXiv2022

Super-resolution trends in the ALMA Taurus survey: Structured inner discs and compact discs

The 1.33 mm survey of protoplanetary discs in the Taurus molecular cloud found annular gaps and rings to be common in extended sources (>~55 au), when their 1D visibility distributions were fit parametrically. We first demonstrate the advantages and limitations of nonparametric visibility fits for data at the survey's 0.12" resolution. Then we use the nonparametric model in Frankenstein ('frank') to identify new substructure in three compact and seven extended sources. Among the new features we identify three trends: a higher occurrence rate of substructure in the survey's compact discs than previously seen, underresolved (potentially azimuthally asymmetric) substructure in the innermost disc of extended sources, and a 'shoulder' on the trailing edge of a ring in discs with strong depletion at small radii. Noting the shoulder morphology is present in multiple discs observed at higher resolution, we postulate it is tracing a common physical mechanism. We further demonstrate how a super-resolution frank brightness profile is useful in motivating an accurate parametric model, using the highly structured source DL Tau in which frank finds two new rings. Finally we show that sparse (u, v) plane sampling may be masking the presence of substructure in several additional compact survey sources.

astro-ph.EP↗

arXiv2022

On the time evolution of the $M_{\rm d} - M_\star$ and $\dot M - M_\star$ correlations for protoplanetary discs: the viscous timescale increases with stellar mass

Large surveys of star-forming regions have unveiled power-law correlations between the stellar mass and the disc parameters, such as the disc mass $M_{\mathrm{d}} \propto {M_{\star}}^{λ_{\mathrm{m}}}$ and the accretion rate $\dot M \propto {M_{\star}}^{λ_{\mathrm{acc}}}$. The observed slopes appear to be increasing with time, but the reason behind the establishment of these correlations and their subsequent evolution is still uncertain. We conduct a theoretical analysis of the impact of viscous evolution on power-law initial conditions for a population of protoplanetary discs. We find that, for evolved populations, viscous evolution enforces the two correlations to have the same slope, $λ_{\mathrm{m}}$ = $λ_{\mathrm{acc}}$, and that this limit is uniquely determined by the initial slopes $λ_{\mathrm{m}, 0}$ and $λ_{\mathrm{acc}, 0}$. We recover the increasing trend claimed from the observations when the difference in the initial values, $δ_0 = λ_{\mathrm{m}, 0} - λ_{\mathrm{acc}, 0}$, is larger than $1/2$; moreover, we find that this increasing trend is a consequence of a positive correlation between the viscous timescale and the stellar mass. We also present the results of disc population synthesis numerical simulations, that allow us to introduce a spread and analyse the effect of sampling, which show a good agreement with our analytical predictions. Finally, we perform a preliminary comparison of our numerical results with observational data, which allows us to constrain the parameter space of the initial conditions to $λ_{\mathrm{m}, 0} \in [1.2, 2.1]$, $λ_{\mathrm{acc}, 0} \in [0.7, 1.5]$.

astro-ph.EP↗

arXiv2021

A super-resolution analysis of the DSHARP survey: Substructure is common in the inner 30 au

The DSHARP survey evidenced the ubiquity of substructure in the mm dust distribution of large, bright protoplanetary discs. Intriguingly, these datasets have yet higher resolution information that is not recovered in a CLEAN image. We first show that the intrinsic performance of the CLEAN algorithm is resolution-limited. Then analyzing all 20 DSHARP sources using the 1D, super-resolution code Frankenstein (frank), we accurately fit the 1D visibilities to a mean factor of 4.3 longer baseline than the Fourier transform of the CLEAN images and a factor of 3.0 longer baseline than the transform of the CLEAN component models. This yields a higher resolution brightness profile for each source, identifying new substructure interior to 30 au in multiple discs; resolving known gaps to be deeper, wider, and more structured; and known rings to be narrower and brighter. Across the survey, high contrast gaps are an average 14% wider and 44% deeper in the frank profiles relative to CLEAN, and high contrast rings are an average 26% narrower. Categorizing the frank brightness profiles into trends, we find that the relative scarcity of features interior to 30 au in the survey's CLEAN images is an artifact of resolving power, rather than an intrinsic rarity of inner disc (or compact disc) substructure. Finally the rings in the frank profiles are narrower than the previously inferred deconvolved widths, indicating smaller alpha / St ratios in the local gas disc.

astro-ph.EP↗

arXiv2021

Multi-wavelength continuum sizes of protoplanetary discs: scaling relations and implications for grain growth and radial drift

We analyse spatially resolved ALMA observations at 0.9, 1.3, and 3.1 mm for the 26 brightest protoplanetary discs in the Lupus star-forming region. We characterise the discs multi-wavelength brightness profiles by fitting the interferometric visibilities in a homogeneous way, obtaining effective disc sizes at the three wavelengths, spectral index profiles and optical depth estimates. We report three fundamental discoveries: first, the millimeter continuum size - luminosity relation already observed at 0.9 mm is also present at 1.3 mm with an identical slope, and at 3.1 mm with a steeper slope, confirming that emission at longer wavelengths becomes increasingly optically thin. Second, when observed at 3.1 mm the discs appear to be only 9% smaller than when observed at 0.9 mm, in tension with models of dust evolution which predict a starker difference. Third, by forward modelling the sample of measurements with a simple parametric disc model, we find that the presence of large grains ($a_\mathrm{max}>1 $mm) throughout the discs is the most favoured explanation for all discs as it reproduces simultaneously their spectral indices, optical depth, luminosity, and radial extent in the 0.9-1.3 mm wavelength range. We also find that the observations can be alternatively interpreted with the discs being dominated by optically thick, unresolved, substructures made of mm-sized grains with a high scattering albedo.

astro-ph.EP↗

arXiv2021

The first ALMA survey of protoplanetary discs at 3 mm: demographics of grain growth in the Lupus region

We present the first ALMA survey of protoplanetary discs at 3 mm, targeting 36 young stellar objects in the Lupus star-forming region with deep observations (sensitivity 20-50 microJy/beam) at ~0.35" resolution (~50 au). Building on previous ALMA surveys at 0.89 and 1.3 mm that observed the complete sample of Class II discs in Lupus at a comparable resolution, we aim to assess the level of grain growth in the relatively young Lupus region. We measure 3 mm integrated fluxes, from which we derive disc-averaged 1-3 mm spectral indices. We find that the mean spectral index of the observed Lupus discs is $α_\mathrm{1-3 mm}=2.23\pm0.06$, in all cases $α_\mathrm{1-3 mm}<3.0$, with a tendency for larger spectral indices in the brightest discs and in transition discs. Furthermore, we find that the distribution of spectral indices in Lupus discs is statistically indistinguishable from that of the Taurus and Ophiuchus star-forming regions. Assuming the emission is optically thin, the low values $α_\mathrm{1-3 mm}\leq 2.5$ measured for most discs can be interpreted with the presence of grains larger than 1 mm. The observations of the faint discs in the sample can be explained without invoking the presence of large grains, namely through a mixture of optically thin and optically thick emission from small grains. However, the bright (and typically large) discs do inescapably require the presence of millimeter-sized grains in order to have realistic masses. Based on a disc mass argument, our results challenge previous claims that the presence of optically thick sub-structures may be a universal explanation for the empirical millimeter size-luminosity correlation observed at 0.89 mm.

astro-ph.EP↗

arXiv2021

Exploring HNC and HCN line emission as probes of the protoplanetary disk temperature

The distributions and abundances of molecules in protoplanetary disks are powerful tracers of the physical and chemical disk structures. The abundance ratios of HCN and its isomer HNC are known to be sensitive to gas temperature. Their line ratios might therefore offer a unique opportunity to probe the properties of the emitting gas. Using the 2D thermochemical code DALI, we ran a set of disk models accounting for different stellar and disk properties, with an updated chemical network for the nitrogen chemistry. These modeling results were then compared with observations, including new ALMA observations of HNC $J=3-2$ for the TW Hya disk and HNC $J=1-0$ for 29 disks in Lupus. Similar to CN, HCN and HNC have brighter line emission in models with larger disk flaring angles and higher UV fluxes. HNC and HCN are predicted to be abundant in the warm surface layer and outer midplane region, which results in ring-shaped emission patterns. However, the precise emitting regions and emission morphology depend on the probed transition, as well as on other parameters such as C and O abundances. The modeled HNC-to-HCN line intensity ratio increases from $<0.1$ in the inner disk to up to 0.8 in the outer disk regions, which can be explained by efficient HNC destruction at high temperatures. Disk-integrated HNC line fluxes from current scarce observations and its radial distribution in the TW Hya disk are broadly consistent with our model predictions. The HNC-to-HCN flux ratio robustly increases with radius (decreasing temperature), but its use as a chemical thermometer in disks is affected by other factors, including UV flux and C and O abundances. High-spatial resolution ALMA disk observations of HNC and HCN that can locate the emitting layers would have the great potential to constrain both the disk thermal and UV radiation structures, and also to verify our understanding of the nitrogen chemistry.

astro-ph.EP↗

arXiv2020

High resolution observations of molecular emission lines toward the CI Tau proto-planetary disc: planet-carved gaps or shadowing?

Recent observations have revealed that most proto-planetary discs show a pattern of bright rings and dark gaps. However, most of the high-resolution observations have focused only on the continuum emission. In this Paper we present high-resolution ALMA band 7 (0.89mm) observations of the disc around the star CI Tau in the $^{12}$CO & $^{13}$CO $J=3$-2 and CS $J=7$-6 emission lines. Our recent work demonstrated that the disc around CI Tau contains three gaps and rings in continuum emission, and we look for their counterparts in the gas emission. While we find no counterpart of the third gap and ring in $^{13}$CO, the disc has a gap in emission at the location of the second continuum ring (rather than gap). We demonstrate that this is mostly an artefact of the continuum subtraction, although a residual gap still remains after accounting for this effect. Through radiative transfer modelling we propose this is due to the inner disc shadowing the outer parts of the disc and making them colder. This raises a note of caution in mapping high-resolution gas emission lines observations to the gas surface density - while possible, this needs to be done carefully. In contrast to $^{13}$CO, CS emission shows instead a ring morphology, most likely due to chemical effects. Finally, we note that $^{12}$CO is heavily absorbed by the foreground preventing any morphological study using this line.

astro-ph.EP↗

arXiv2020

Frankenstein: Protoplanetary disc brightness profile reconstruction at sub-beam resolution with a rapid Gaussian process

Interferometric observations of the mm dust distribution in protoplanetary discs are now showing a ubiquity of annular gap and ring substructures. Their identification and accurate characterization is critical to probing the physical processes responsible. We present Frankenstein (frank), an open source code that recovers axisymmetric disc structures at sub-beam resolution. By fitting the visibilities directly, the model reconstructs a disc's 1D radial brightness profile nonparametrically using a fast (<~1 min) Gaussian process. The code avoids limitations of current methods that obtain the radial brightness profile by either extracting it from the disc image via nonlinear deconvolution at the cost of reduced fit resolution, or by assumptions placed on the functional forms of disc structures to fit the visibilities parametrically. We use mock ALMA observations to quantify the method's intrinsic capability and its performance as a function of baseline-dependent signal-to-noise. Comparing the technique to profile extraction from a CLEAN image, we motivate how our fits accurately recover disc structures at a sub-beam resolution. Demonstrating the model's utility in fitting real high and moderate resolution observations, we conclude by proposing applications to address open questions on protoplanetary disc structure and processes.

astro-ph.EP↗

arXiv2020

The evolution of dust-disk sizes from a homogeneous analysis of 1-10 Myr-old stars

We utilize ALMA archival data to estimate the dust disk size of 152 protoplanetary disks in Lupus (1-3 Myr), Chamaeleon I (2-3 Myr), and Upper-Sco (5-11 Myr). We combine our sample with 47 disks from Tau/Aur and Oph whose dust disk radii were estimated, as here, through fitting radial profile models to visibility data. We use these 199 homogeneously derived disk sizes to identify empirical disk-disk and disk-host property relations as well as to search for evolutionary trends. In agreement with previous studies, we find that dust disk sizes and millimeter luminosities are correlated, but show for the first time that the relationship is not universal between regions. We find that disks in the 2-3 Myr-old Cha I are not smaller than disks in other regions of similar age, and confirm the Barenfeld et al. (2017) finding that the 5-10 Myr USco disks are smaller than disks belonging to younger regions. Finally, we find that the outer edge of the Solar System, as defined by the Kuiper Belt, is consistent with a population of dust disk sizes which have not experienced significant truncation.

astro-ph.EP↗

arXiv2019

Detecting the halo heating from AGN feedback with ALMA

The Sunyaev-Zel'dovich (SZ) effect can potentially be used to investigate the heating of the circumgalactic medium and subsequent suppression of cold gas accretion onto the host galaxy caused by quasar feedback. We use a deep ALMA observation of HE0515-4414 in band 4, the most luminous quasar known at the peak of cosmic star formation (z=1.7), to search for the SZ signal tracing the heating of the galaxy's halo. ALMA's sensitivity to a broad range of spatial scales enables us to disentangle emitting compact sources from the negative, extended SZ signal. We obtain a marginal S-Z detection (~3.3$σ$) on scales of about 300 kpc (30-40 arcsec), at the 0.2 mJy level, 0.5 mJy after applying a correction factor for primary beam attenuation and flux that is resolved out by the array. We show that our result is consistent with a simulated ALMA observation of a similar quasar in the FABLE cosmological simulations. We emphasise that detecting an SZ signal is more easily achieved in the visibility plane than in the (inferred) images. We also confirm a marginal detection (3.2$σ$) of a potential SZ dip on smaller scales (<100 kpc) already claimed by other authors, possibly highlighting the complex structure of the halo heating. Finally, we use SZ maps from the FABLE cosmological simulations, convolved with ALMA simulations, to illustrate that band 3 observations are much more effective in detecting the SZ signal with higher significance, and discuss the optimal observing strategy.

astro-ph.GA↗

arXiv2019

Compact Disks in a High Resolution ALMA Survey of Dust Structures in the Taurus Molecular Cloud

We present a high-resolution ($\sim0.''12$, $\sim16$ au, mean sensitivity of $50~μ$Jy~beam$^{-1}$ at 225 GHz) snapshot survey of 32 protoplanetary disks around young stars with spectral type earlier than M3 in the Taurus star-forming region using Atacama Large Millimeter Array (ALMA). This sample includes most mid-infrared excess members that were not previously imaged at high spatial resolution, excluding close binaries and highly extincted objects, thereby providing a more representative look at disk properties at 1--2 Myr. Our 1.3 mm continuum maps reveal 12 disks with prominent dust gaps and rings, 2 of which are around primary stars in wide binaries, and 20 disks with no resolved features at the observed resolution (hereafter smooth disks), 8 of which are around the primary star in wide binaries. The smooth disks were classified based on their lack of resolved substructures, but their most prominent property is that they are all compact with small effective emission radii ($R_{\rm eff,95\%} \lesssim 50$ au). In contrast, all disks with $R_{\rm eff,95\%}$ of at least 55 au in our sample show detectable substructures. Nevertheless, their inner emission cores (inside the resolved gaps) have similar peak brightness, power law profiles, and transition radii to the compact smooth disks, so the primary difference between these two categories is the lack of outer substructures in the latter. These compact disks may lose their outer disk through fast radial drift without dust trapping, or they might be born with small sizes. The compact dust disks, as well as the inner disk cores of extended ring disks, that look smooth at the current resolution will likely show small-scale or low-contrast substructures at higher resolution. The correlation between disk size and disk luminosity correlation demonstrates that some of the compact disks are optically thick at millimeter wavelengths.

astro-ph.SR↗