Research highlights
May 2023
ERC WANDA is now one year old!
The ERC WANDA team has grown in this year with 4 new hirings (see https://www.eso.org/~cmanara/wanda_erc.html#team).
A lot of new exciting results are already coming out, see https://www.eso.org/~cmanara/wanda_erc.html#results
November 2022
Fall Colloquium at STScI
I gave the Fall Colloquium at STScI, which was recorded and can be seen here: https://www.stsci.edu/contents/events/stsci/2022/november/demographics-of-young-stars-and-their-protoplanetary-disks
Enjoy!
May 2022
ERC WANDA has started!
Now that I am leading the ERC WANDA team, most recent results will appear on the teams' website: https://www.eso.org/~cmanara/wanda_erc.html#results
Check it out!
September 2021
Paper II of PENELLOPE
Our paper2 of the ESO/VLT Large Program PENELLOPE is out!
We discuss the properties of a newly discovered spectroscopic binary target in Orion OB1. We can infer the properties of this target from the RV measurements from our UVES and X-Shooter data.
March 2021
First results from PENELLOPE
Our paper1 of the ESO/VLT Large Program PENELLOPE is out!
We present survey strategy, data analysis, and first results on accretion properties in Orion OB1 and sigma-Ori, with a quick comparison with HST data.
Data are all available at: ZENODO
ADS+ link: Manara, Frasca et al. 2021 A&A, in press
June 2020
There is enough mass to form planets!
While we have shown that by 2-3 Myr, in the Class II phase, the mass of protoplanetary disks is not sufficient to explain the observed exoplanet population (Manara et al. 2018), in this work we show that at earlier ages, during the Class 0 and I phase, the disks are massive enough to agree with planet formation models assuming efficiency of ~10-30%, depending on the models. Is planet formation happening extremely fast?
ADS+ link: Tychoniec, Manara, Rosotti et al. 2020 A&A, in press
Some news items: Science Mag: Baby planets are born exceptionally fast
NOVA: Planets must be formed early
May 2020
Accretion rates at ages>5 Myr: Upper Scorpius
While it is expected by viscous evolution that accretion rates decrease with time and their relation with disk masses becomes tighter at age>3 Myr, our investigation of 36 young stars with disks in the 5-10 Myr old Upper Scorpius region reveals a different reality. Accretion rates are still high, and the spread of Macc-Mdisk large. This might point to the need to account for dust evolution to describe observations of disks, and also to the limit of viscous evolution theory.
November 2019
Comparing observations with models of planet population synthesis
Planet population synthesis simulations are based on assumptions on the protoplanetary disk structure at the time of planet formation. We test here whether these assumptions are in agreement with current observations of disk mass and mass accretion rates. While an overall agreement is found, the spread of the relation in the models is smaller than in the data, and the number of giant-forming disks with low accretion rates and high disk masses is too high in the models. This test can be used to further constrain models in the future.
ADS+ link: Manara, Mordasini, Testi et al. 2019, A&A, 631, L2
July 2019
ALMA view of disks in multiple stellar systems in the Taurus region
We observed 10 multiple stellar systems at spatial resolution of ~0.1" in the Taurus region with ALMA. We find that disks in binaries are smaller than around singles, they have steeper outer edges, and their sizes are compatible with tidal truncation models only for high eccentricities
ADS+ link: Manara, Tazzari, Long, Herczeg et al. 2019, A&A, 628, A95
Other paper on our ALMA Taurus survey:
disks with gaps/rings: Long et al. 2018
smooth disks: Long et al. 2019
MWC480: Liu et al. 2019
planet embedded in disks: Lodato et al. 2019
May 2019
An extreme difference between gas and dust size in a faint protoplanetary disk
The faint (10 mJy) protoplanetary disk around CX Tau shows a very large (>5) ratio between the gas and dust disk size, most probably due to radial drift in a disk with NO RINGS/STRUCTURES! Are all faint disks like this?
ADS+ link: Facchini, van Dishoeck, Manara, et al. 2019, A&A Letter, in press
April 2019
Low mass disks in the Corona Australis region
Our survey of protoplanetary disks in the ~1 Myr Corona Australis region shows a puzzling low mass of the disk population. Our assessment of the stellar properties seems to confirm that these objects are young. One possible solution could be that these disks are born small. This suggests that the initial conditions for disk formation may be very different in each region, and they might have a very important role in shaping disk evolution.
ADS+ link: Cazzoletti, Manara, Liu, et al. 2019, A&A, in press
September 2018
Why do protoplanetary disks appear not massive enough to form the known exoplanet population?
We combined recent ALMA surveys of protoplanetary disks (revised with new Gaia DR2 distances) with the state-of-the-art of exoplanet surveys. We find that there is not enough mass in disks at 1-3 Myr to explain exoplanetary systems, even when considering the mass in solids in disks vs the mass of solids in planets. This is now true for a large range of stellar masses covered both in disks and exoplanet surveys.
Possible solutions, unless protoplanetary disk masses are heavily underestimated (but I have reasons to believe this is not the case) are:
1) cores of planets have formed very rapidly (<0.1-1 Myr)
2) disks are continuously replenished of fresh planet-forming material from the environment
ADS+ link: Manara, Morbidelli, Guillot 2018, A&A Letter
Some news items: Cosmic Conundrum (ScienceMag)
Planets found to be larger than... (QuantaMagazine)
June 2018
A solution to the long-lasting questions on the low disk fraction of the Lupus V-VI clouds
The Spitzer Gould Belt Survey found in the Lupus V-VI clouds an unexpected low fraction of stars with protoplanetary disks (~10-20%; Spezzi et al. 2011; Dunham et al. 2015) given the assumed age of the region (~2 Myr). Little spectroscopic follow-up has been carried out to confirm the status of young stellar objects (YSOs) of the YSO candidates identified with Spitzer.
The recently released Gaia DR2 catalog has allowed us to finally give a clear solution to this conundrum of this low disk fraction: only 5 candidate YSOs in the Lupus V clouds have parallaxes compatible with the distance of the Lupus clouds. The other candidates in this cloud and in Lupus VI are background giants, as seen from their position on the CMD.
This clarifies that the disk fraction measured in this region was highly contaminated by background objects and that these two clouds can actually be 'sterile', in line with the measured Av<6 mag.
December 2017
A revised distance to the clouds in the Chamaeleon star-forming region
We have used Gaia DR1 TGAS parallaxes for stars located on the line of sight of the dark clouds in the Chamaeleon star-forming region to determine the distance of these clouds. When combining the parallax measurements with estimates of the color excess of a star, we are able to identify the distance of a cloud as the distance where there is a significative increase of the color excess. We measure a new distance to the Chamaeleon I cloud of 180 pc, 20 pc further away than previously assumed. We confirm a distance of 180 pc for the Chamaeleon II cloud, and we measure for the first time the distance to the Chamaeleon III cloud, which is 193 pc. Gaia DR2 will allow us to use more confirmed members of the region to further constrain these distances and the 3D structure of the region.
ADS link: Voirin, Manara, Prusti 2017, A&A
December 2017
Constraints on viscous evolution theory combining mass accretion rate and disk mass measurements
We have further explored the observed relation between mass accretion rates and disk mass. As in the Lupus star-forming region (Manara et al. 2016b), also in the Chamaeleon I region the two quantities are correlated (Mulders et al. 2017). However, the slope is slightly shallower than linear, and the spread is larger than expected from alpha-constant viscous evolution models (Mulders et al. 2017). With two independent analysis we have shown that the observed relation can be reproduced by viscous models assuming that the initial viscous timescales of the disks are of about 1 Myr, thus of the order of the age of the star-forming regions observed (Lodato et al. 2017, Mulders et al. 2017). Study must be done to understand also how this relation can constrain other disk evolution theories.
ADS links: Mulders, Pascucci, Manara et al. 2017, ApJ;
April 2017
Measurements of mass accretion rates in complete samples of nearby star forming regions: a break in the accretion vs stellar mass relation?
We have completed the VLT/X-Shooter surveys of the Chamaeleon I and Lupus star forming regions. The analysis of these close-to-complete samples has shown that the relation between the mass accretion rate onto the central star and the stellar mass is described with either a single power-law with exponent ~2, as found it the past, or with a broken power-law with a steeper slope for lower mass stars, although none of the two possibilities can be statistically excluded. In the latter case, a possible explanation is that disks around low mass stars evolve faster, or that accretion is driven by different processes at different stellar masses.
ADS links:
Chamaeleon I - Manara, Testi et al. 2017, A&A, 604, A127;
Lupus - Alcala, Manara et al. 2017, A&A, 600, 20.
March 2017
Constraining proto-planetary disk evolution using accretion rate and disk mass measurements
We present the theoretical description of how measurements of protoplanetary disk masses and accretion rates provided by surveys of star forming regions can be analysed via the dimensionless accretion parameter, which we define as the product of the accretion rate and stellar age divided by the disc mass. We extend and generalize the study of Jones et al (2012) demonstrating that this parameter should be less than or of order unity for a wide range of evolutionary scenarios, rising above unity only during the final stages of outside in clearing by external photoevaporation. We use this result to show that while dust based mass estimates produce results compatible with theoretical expectations assuming canonical dust/gas ratio, the systematically lower CO based disk mass estimates yield accretion efficiencies significantly above unity in contrast with the theory. This finding provides additional evidence that CO based disk masses are an under-estimate, in line with arguments that have been made on the basis of chemical modelling of relatively small samples. On the other hand, we demonstrate that dust based disk mass estimates are sufficiently accurate to reveal distinctly higher accretion efficiencies in the Trapezium cluster, where this result is expected given the evident importance of external photoevaporation. We therefore propose the dimensionless accretion parameter as a new diagnostic of external photoevaporation in other star forming regions.
ADS link: Rosotti, Clarke, Manara, and Facchini, 2017, MNRAS, 468, 1631
March 2017
New Evidence for the Dynamical Decay of a Multiple System in the Orion Kleinmann-Low Nebula
Using two epochs of observations with the Hubble Space Telescope we have measured astrometry for members of the Orion Nebula Cluster. We have discovered that a star in the Kleinmann-Low Nebula, source x from Lonsdale et al. (1982), is moving with an unusually high proper motion of 29 mas/yr, which corresponds to 55 km/s at the distance of Orion. Previous radio observations have found that three other stars in the Kleinmann-Low Nebula (BN and sources I and n) have high proper motions (5-14 mas/yr) and were near a single location ~540 years ago, and thus may have been members of a multiple system that dynamically decayed. The proper motion of source x is consistent with ejection from that same location 540 years ago, which provides strong evidence that the dynamical decay did occur and that the runaway star BN originated in the Kleinmann-Low Nebula rather than the nearby Trapezium cluster. This result is the first coming from our recent HST Treasury program in the ONC (PI Robberto).
ADS link: Luhman et al. 2017, ApJL, 838, L3
Check these out: Hubble news, Space Telescope news, Media INAF, Polluce Notizie.
December 2016
Ringed Structures of the HD 163296 Protoplanetary Disk Revealed by ALMA
We observed the protoplanetary disk around the Herbig Ae star HD 163296 with ALMA with a resolution as small as 25 au, both in the 1.3 mm continuum emission and in the CO isotopologues. The continuum map shows three dark concentric rings at about 60, 100, and 160 au from the central star. By comparing the observations with theoretical models for the disk emission, we find that the density of CO molecules is reduced inside the middle and outer dust gaps. However, in the inner ring there is no evidence of CO depletion. From the measurements of the dust and gas densities, we deduce that the gas-to-dust ratio varies across the disk and, in particular, it increases by at least a factor 5 within the inner dust gap compared to adjacent regions of the disk. The depletion of both dust and gas suggests that the middle and outer rings could be due to the gravitational torque exerted by two Saturn-mass planets orbiting at 100 and 160 A.U. from the star. On the other hand, the inner dust gap could result from dust accumulation at the edge of a magnetorotational instability dead zone, or from dust opacity variations at the edge of the CO frost line.
PRL link: Isella et al. 2016, Phys. Rev. Lett. 117, 251101
Check these out: Physics viewpoint, Media INAF, Google!
October 2016
The violent environment of the inner disk of RW Aur A probed by the 2010 and 2015 dimming events
We have observed with the VLT/X-Shooter spectrograph the primary star of the young binary system RW Aur during its recent deep dimming event. By comparing this spectrum with observations taken before the dimming event we have shown evidence of a variation in the shape of the absorption feature of the NaD at v~-60 km/s, which indicates that during the dim state the disk wind is either enhanced, or significantly displaced into the line of sight. We conclude that the dimming event is related to a major perturbation on the inner disk. We suggest that the inner disk is occulting (most of) the star, and thus its photosphere, but is not occulting the accretion regions within a few stellar radii. In this picture, the inner disk must be warped with respect to the outer disk.
September 2016
The peculiar dipping of the young star EPIC 204278916
We have serendipitously discovered EPIC 204278916 from its K2 light curve, which displays irregular dimming of up to 65% for ~25 consecutive days out of ~80 days of observations. After this dimming event the light curve displays regular variability, which we attribute to stellar rotation. This star is young, low mass (M-type), and still surrounded by a disk, as we show using ALMA observations. We hypothesise that the irregular dimmings are caused by either a warped inner-disk edge or transiting cometary-like objects in either circular or eccentric orbits. This object is now a new member of the well known "YSO-dippers" class.
ADS link: Scaringi, Manara, et al. 2016, MNRAS, 463, 2265
One nice article for the general public can be found here. But check also here.
May 2016
Relation between disk mass and mass accretion rates
We have combined the disk mass measured with ALMA (Ansdell et al. 2016) and the mass accretion rates measured with X-Shooter spectra (Alcala et al. 2014, 2016 subm.) for 66 targets in the Lupus star forming region. We find a correlation between these quantities, as predicted in the context of viscous evolution of disks, but only when using the dust disk mass and not when using the gas disk mass. The lack of correlation when using gas disk masses, as well as the small values of the disk mass to mass accretion rate measured using the gas disk mass, suggest that the CO disk mass might underestimate the total disk mass, or that other external disturbances to the disk evolution are happening.ADS link: Manara et al. 2016, A&A Letter
Presentation of the paper on Astrobites and in Astrobites en español.
May-August 2016 - December 2016
ALMA surveys of protoplanetary disks: Lupus & Chamaeleon I
The unprecedented sensitivity and resolution of ALMA is giving us a new view of protoplanetary disks. In particular, surveys of complete samples of disks in different nearby star forming regions are showing us a variety of disk properties, from different morphologies to different gas-to-dust ratios from one disk to another. Both in our large survey in the Lupus region (Ansdell et al. 2016) and in the Chamaeleon I region (Pascucci et al. 2016) we find a correlation between the amount of dust in the disk and the stellar masses derived using the VLT/X-Shooter spectra. This correlation is less steep than the one measured by other teams in the older Upper Scorpius region (Barenfeld et al. 2016) and similar to the one measured in the Taurus cloud (Andrews et al. 2013).
The unexpected low gas-to-dust ratios we measure are opening new questions on the physical or chemical evolution of disks (Miotello et al. 2017), and our future approved ALMA programs will help us to deepen our understanding of this and other open questions on disk evolution.
January 2016
Stellar and accretion properties of young stars
We are collecting samples of VLT/X-Shooter spectra of young stars with disks in different nearby regions to derive their stellar, accretion, and wind properties. The spectra are analyzed with the method we have developed to simultaneously derive stellar and accretion properties. We have studied targets in the very young ρ-Ophiucus cluster (Manara et al. 2015), in the slightly older Lupus (Alcala et al. 2014, 2017 in prep.) and Chamaeleon I (Manara et al. 2016a, 2017 in prep.) regions, and in the old TWA association (Stelzer et al. in prep.). We have studied how mass accretion correlates with stellar mass, and derived homogeneously stellar and accretion parameters for all the targets to be used together with their disk properties.
June 2014
Accretion properties of transitional disks
We have analyzed a sample of 22 X-Shooter spectra of transitional disks to determine their stellar and accretion properties. Our analysis has shown that there are (at least) some transitional disks with mass accretion rates as high as those of classical T Tauri stars.
This suggests that the innermost part of the disk of these objects is gas rich and that this gas reservoir needs to be refurnished even through a dust depleted gap.
ADS link: Manara et al. 2014, A&A, 568, 18
July 2013
Accurate determination of stellar and accretion rates in young stars
To analyze two major age-outliers in the Orion Nebula Cluster (ONC), we have developed an automatic procedure to determine self-consistently stellar and accretion properties of young stellar objects from broad-band, medium-resolution spectra obtained with the VLT/X-Shooter spectrograph. Our analysis is based on a multicomponent fit that includes the photospheric emission using a set of photospheric templates (Manara et al. 2013a), the effect of reddening, and the continuum excess due to accretion with a set of isothermal slab models. This procedure allows us to resolve degeneracies between various parameters, such as extinction and accretion excess, to determine the real properties of the targets.
In this study we have shown that this analysis leads to an age determination for the two targets consistent with the typical age of objects located in the ONC.
ADS link: Manara et al. 2013b, A&A, 558, 114
