The GRAVITY Young Stellar Object survey

Context. The formation and the evolution of protoplanetary disks are important stages in the lifetime of stars. Terrestrial planets form or migrate within the innermost regions of these protoplanetary disks and so, the processes of disk evolution and planet formation are intrinsically linked. Studies of the dust distribution, composition, and evolution of these regions are crucial to understanding planet formation. Aims. We built a homogeneous observational dataset of Herbig Ae/Be disks with the aim of spatially resolving the sub au-scale region to gain a statistical understanding of their morphological and compositional properties, in addition to looking for correlations with stellar parameters, such as luminosity, mass, and age. Methods. We observed 27 Herbig Ae/Be stars with the GRAVITY instrument installed at the combined focus of the Very Large Telescope Interferometer (VLTI) and operating in the near-infrared K-band, focused on the K-band thermal continuum, which corresponds to stellar flux reprocessed by the dust grains. Our sample covers a large range of effective temperatures, luminosities, masses, and ages for the intermediate-mass star population. The circumstellar disks in our sample also cover a range of various properties in terms of reprocessed flux, flared or flat morphology, and gaps. We developed semi-physical geometrical models to fit our interferometric data. Results. Our best-fit models correspond to smooth and wide rings that support previous findings in the H-band, implying that wedge-shaped rims at the dust sublimation edge are favored. The measured closure phases are generally non-null with a median value of ~10°, indicating spatial asymmetries of the intensity distributions. Multi-size grain populations could explain the closure phase ranges below 20–25° but other scenarios should be invoked to explain the largest ones. Our measurements extend the Radius-Luminosity relation to ~104 L⊙ luminosity values and confirm the significant spread around the mean relation observed by PIONIER in the H-band. Gapped sources exhibit a large N-to-K band size ratio and large values of this ratio are only observed for the members of our sample that would be older than 1 Ma, less massive, and with lower luminosity. In the mass range of 2 M⊙, we do observe a correlation in the increase of the relative age with the transition from group II to group I, and an increase of the N-to-K size ratio. However, the size of the current sample does not yet permit us to invoke a clear, universal evolution mechanism across the Herbig Ae/Be mass range. The measured locations of the K-band emission in our sample suggest that these disks might be structured by forming young planets, rather than by depletion due to EUV, FUV, and X-ray photo-evaporation.

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VISION – Vienna survey in Orion

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832577 ◽

2019 ◽

Vol 622 ◽

pp. A149 ◽

Cited By ~ 14

Author(s):

Josefa Elisabeth Großschedl ◽

João Alves ◽

Paula S. Teixeira ◽

Hervé Bouy ◽

Jan Forbrich ◽

...

Keyword(s):

Main Sequence ◽

Near Infrared ◽

Far Infrared ◽

Circumstellar Disks ◽

Mass Star ◽

Main Sequence Stars ◽

Star Forming ◽

Spatial Coverage ◽

Significant Difference ◽

Infrared Data

We have extended and refined the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3 deg2, ∼950 pc2), seeing limited resolution (∼0.7″), and sensitivity (Ks < 19 mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ∼6.4% and ∼2.3%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A’s low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2980 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 185 flat-spectrum sources, and 2607 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.

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The Onset of Planet Formation in Brown Dwarf Disks

Science ◽

10.1126/science.1118042 ◽

2005 ◽

Vol 310 (5749) ◽

pp. 834-836 ◽

Cited By ~ 140

Author(s):

Dániel Apai ◽

Ilaria Pascucci ◽

Jeroen Bouwman ◽

Antonella Natta ◽

Thomas Henning ◽

...

Keyword(s):

Infrared Spectra ◽

Planet Formation ◽

Protoplanetary Disks ◽

Brown Dwarfs ◽

Circumstellar Disks ◽

Dust Grains ◽

Brown Dwarf ◽

Intermediate Mass ◽

Intermediate Mass Stars ◽

Robust Process

The onset of planet formation in protoplanetary disks is marked by the growth and crystallization of sub–micrometer-sized dust grains accompanied by dust settling toward the disk mid-plane. Here, we present infrared spectra of disks around brown dwarfs and brown dwarf candidates. We show that all three processes occur in such cool disks in a way similar or identical to that in disks around low- and intermediate-mass stars. These results indicate that the onset of planet formation extends to disks around brown dwarfs, suggesting that planet formation is a robust process occurring in most young circumstellar disks.

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Radio Interferometry Observations of the Hallmarks of Planet Formation

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313007977 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 80-89

Author(s):

Sean M. Andrews

Keyword(s):

Planet Formation ◽

Angular Resolution ◽

Planetary System ◽

Planetary Systems ◽

Protoplanetary Disks ◽

Circumstellar Disks ◽

High Angular Resolution ◽

Radio Interferometry ◽

New Directions ◽

And Migration

AbstractSome of the fundamental processes involved in the evolution of circumstellar disks and the assembly of planetary systems are just now becoming accessible to astronomical observations. The new promise of observational work in the field of planet formation makes for a very dynamic research scenario, which is certain to be amplified in the coming years as the revolutionary Atacama Large Millimeter/submillimeter Array (ALMA) facility ramps up to full operations. To highlight the new directions being explored in these fields, this brief review will describe how high angular resolution measurements at millimeter/radio wavelengths are being used to study several crucial aspects of the formation and early evolution of planetary systems, including: the gas and dust structures of protoplanetary disks, the growth and migration of disk solids, and the interactions between a young planetary system and its natal, gas-rich disk.

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Do Herbig Ae/Be Stars Have Disks?

International Astronomical Union Colloquium ◽

10.1017/s0252921100043141 ◽

1997 ◽

Vol 163 ◽

pp. 525-530 ◽

Cited By ~ 1

Author(s):

T.P. Ray ◽

M. Corcoran

Keyword(s):

Equivalent Width ◽

Near Infrared ◽

Mass Loss Rate ◽

Line Emission ◽

Circumstellar Disks ◽

T Tauri Stars ◽

Be Stars ◽

Infrared Excess ◽

T Tauri ◽

Outflow Rate

AbstractThe Herbig Ae/Be stars are optically visible pre-main sequence stars of intermediate mass (M* ≈ 3−8M⊙) and are thought to be the higher mass analogues of the T Tauri stars. While there is no doubt that classical T Tauri stars, i.e. those with EW(Hα) ≳ 10 Å, are surrounded by disks, it remains controversial as to whether this is the case with the equivalent Herbig Ae/Be stars. It has even been questioned whether the powerful winds that are ejected by Herbig Ae/Be stars are driven by accretion. To address these problems we have examined a large sample of these stars with the idea of using their forbidden line emission as an indirect diagnostic for the presence of disks. Striking similarities with the classical T Tauri stars are found. For example we have discovered evidence not only for a strong correlation between near-infrared colours and the equivalent width of the forbidden line emission but also that the forbidden line emission normally arises in a blueshifted outflow component. It has already been shown in the case of the classical T Tauri stars that the correlation of near-infrared colour with forbidden line equivalent width is due to a link between the accretion rate and the outflow rate. The virtually identical relationship seen in the case of the Herbig Ae/Be stars must then also have a similar origin. Our finding that the forbidden line emission in Herbig Ae/Be stars is normally blueshifted shows not only that it arises in an outflow but, as in the classical T Tauri stars, such an asymmetry in the velocity centre of the line must be caused by the obscuring effects of a disk. We find that the correlation seen in the classical T Tauri stars between the mass-loss rate and infrared excess can be extended, when we include the Herbig Ae/Be stars, to cover almost 5 orders of magnitude in stellar luminosity. Our observations therefore broaden the findings of earlier observers for low mass young stars and indicate the presence of circumstellar disks around the majority of Herbig Ae/Be stars with forbidden line emission. A corollary of our results is that the same outflow mechanism must operate in both the classical T Tauri stars and the Herbig Ae/Be stars with forbidden line emission.

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A giant exoplanet orbiting a very-low-mass star challenges planet formation models

Science ◽

10.1126/science.aax3198 ◽

2019 ◽

Vol 365 (6460) ◽

pp. 1441-1445 ◽

Cited By ~ 22

Author(s):

J. C. Morales ◽

A. J. Mustill ◽

I. Ribas ◽

M. B. Davies ◽

A. Reiners ◽

...

Keyword(s):

Near Infrared ◽

Planet Formation ◽

Giant Planet ◽

Mass Star ◽

Low Mass Stars ◽

Migration Rates ◽

Low Mass ◽

And Migration ◽

Core Accretion ◽

Planet Accretion

Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.

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Simultaneous Visible and Near-Infrared Variability of Classical T Tauri Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313008144 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 149-150

Author(s):

Yukako Aimi ◽

Misato Fukagawa ◽

Tomonori Yasuda ◽

Takuya Yamashita ◽

Kouji Kawabata ◽

...

Keyword(s):

Hot Spots ◽

Structural Changes ◽

Near Infrared ◽

Protoplanetary Disks ◽

Circumstellar Matter ◽

T Tauri Stars ◽

The Other ◽

Stellar Systems ◽

Be Stars ◽

T Tauri

AbstractTemporal structural changes of protoplanetary disks surrounding T Tauri stars (TTSs) can cause magnitude variations of TTSs. On the other hand, variability is also expected due to cool spots and/or hot spots on the surface of the star, thus it is important to distinguish the causes of the observed variability. Our sample consists of 23 TTSs (22 classical T Tauri stars, 1 weak-lined T Tauri star) and 4 Herbig Ae/Be stars. The observations were performed over a period of about 3 months in the V, J, and KS band, simultaneously. We detected variability for all stars in the three bands (>0.05 mag in V, >0.09 mag in J, >0.09 mag in KS). Color-magnitude relations obtained between V, J, and KS bands suggest that stellar spots are not the only cause of variability for most of our targets. In addition, the data implies that six stellar systems contain larger grains than in the interstellar medium if the variability is only caused by extinction due to circumstellar matter.

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The Structure and Evolution of Protoplanetary Disks: an Infrared and Submillimeter View

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006249 ◽

2015 ◽

Vol 10 (S314) ◽

pp. 128-134

Author(s):

Lucas A. Cieza

Keyword(s):

Formation Process ◽

Extrasolar Planets ◽

Planet Formation ◽

Planetary Systems ◽

Protoplanetary Disks ◽

Circumstellar Disks ◽

Submillimeter Wavelength ◽

High Incidence ◽

Near Future ◽

Very High

AbstractCircumstellar disks are the sites of planet formation, and the very high incidence of extrasolar planets implies that most of them actually form planetary systems. Studying the structure and evolution of protoplanetary disks can thus place important constraints on the conditions, timescales, and mechanisms associated with the planet formation process. In this review, we discuss observational results from infrared and submillimeter wavelength studies. We review disk lifetimes, transition objects, disk demographics, and highlight a few remarkable results from ALMA Early Science observations. We finish with a brief discussion of ALMA's potential to transform the field in near future.

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SpS1-Dust and gas clearing in transitional disks

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310010483 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 521-521

Author(s):

Joanna M. Brown

Keyword(s):

Planet Formation ◽

Giant Planet ◽

Circumstellar Disks ◽

Spectral Energy ◽

Mass Star ◽

Infrared Observations ◽

Star Forming ◽

Star Forming Regions ◽

Disk Material ◽

Low Mass

Understanding how disks dissipate is essential to studies of planet formation. Infrared observations of young stars demonstrate that optically-thick circumstellar disks disappear from around half the stars in low-mass star-forming regions by an age of 3 Myr and are almost entirely absent in 10 Myr old associations (e.g. Haisch et al., 2001). Accretion ceases on the same approximate timescale (e.g. Calvet et al. 2005). The disappearence of gas and dust - planetary building material - places stringent limits on the timescales of giant planet formation. During this crucial interval, planet(esimal)s form and the remaining disk material is accreted or dispersed. Mid-infrared spectrophotometry of protoplanetary disks has revealed a small sub-class of objects in the midst of losing their disk material. These disks have spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content, often interpreted as a signature of young planets. Such objects are still rare although Spitzer surveys have significantly increased the number of known transitional objects (e.g. Brown et al. 2007, D'Alessio et al., 2005). However, spectrophotometric signatures are indirect and notoriously difficult to interpret as multiple physical scenarios can result in the same SED. Recent direct imaging from millimeter interferometry has confirmed the presence of large inner holes in transitional disks, providing additional constraints and lending confidence to current SED interpretations (Brown et al. 2008, Brown et al. 2009, Andrews et al. 2009, Isella et al., 2009).

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How to identify magnetic field activity in young circumstellar disks

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900379x ◽

2018 ◽

Vol 14 (A30) ◽

pp. 126-127

Author(s):

Mario Flock ◽

Gesa H.-M. Bertrang

Keyword(s):

Magnetic Field ◽

Near Infrared ◽

Dynamical Evolution ◽

Protoplanetary Disks ◽

Circumstellar Disks ◽

Toroidal Magnetic Field ◽

Rotational Instability ◽

Polarization Pattern ◽

Poloidal Magnetic Field ◽

Field Activity

AbstractRecent advanced simulations of protoplanetary disks allow us to search for observational constraints to identify the magnetic field activity in protoplanetary disks. With our 3D radiation non-ideal magneto-hydrodynamical (MHD) models including irradiation from an Herbig type star we are able to model the thermal and dynamical evolution in a so far never reached detail (Flock et al. 2017). The activity of the magneto-rotational instability in the inner hot ionized regions comes along with a magnetic dynamo. The oscillations in the mean toroidal magnetic field with a timescale of 10 local orbits can slightly bend the inner dust rim and so the irradiation surface. This causes a clear variability pattern in the near infrared (NIR) emission at the dust inner rim surface. Another way to identify the presence of magnetic fields are to search for polarization signatures. Using 3D non-ideal MHD simulations of the outer disk regions (Flock et al. 2015) we calculate synthetic images of the intrinsically polarized continuum emitted by aspherical grain aligned with the dominantly toroidal magnetic field (Bertrang et al. 2017). Our results show a clear radial polarization pattern for face-on observed disk, similar to recent observations by Ohashi et al. (2018). Additionally, we are even able to see the change of the polarization pattern inside the vortex as the poloidal magnetic field dominates therein.

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An optical observational cluster mass function at z ∼ 1 with the ORELSE survey

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab300 ◽

2021 ◽

Vol 502 (3) ◽

pp. 3942-3954

Author(s):

D Hung ◽

B C Lemaux ◽

R R Gal ◽

A R Tomczak ◽

L M Lubin ◽

...

Keyword(s):

Monte Carlo ◽

Large Scale ◽

Near Infrared ◽

Function Analysis ◽

Voronoi Tessellation ◽

Cosmological Parameters ◽

Mass Range ◽

Mass Function ◽

Cluster Mass ◽

Theoretical Mass

ABSTRACT We present a new mass function of galaxy clusters and groups using optical/near-infrared (NIR) wavelength spectroscopic and photometric data from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. At z ∼ 1, cluster mass function studies are rare regardless of wavelength and have never been attempted from an optical/NIR perspective. This work serves as a proof of concept that z ∼ 1 cluster mass functions are achievable without supplemental X-ray or Sunyaev-Zel’dovich data. Measurements of the cluster mass function provide important contraints on cosmological parameters and are complementary to other probes. With ORELSE, a new cluster finding technique based on Voronoi tessellation Monte Carlo (VMC) mapping, and rigorous purity and completeness testing, we have obtained ∼240 galaxy overdensity candidates in the redshift range 0.55 < z < 1.37 at a mass range of 13.6 < log (M/M⊙) < 14.8. This mass range is comparable to existing optical cluster mass function studies for the local universe. Our candidate numbers vary based on the choice of multiple input parameters related to detection and characterization in our cluster finding algorithm, which we incorporated into the mass function analysis through a Monte Carlo scheme. We find cosmological constraints on the matter density, Ωm, and the amplitude of fluctuations, σ8, of $\Omega _{m} = 0.250^{+0.104}_{-0.099}$ and $\sigma _{8} = 1.150^{+0.260}_{-0.163}$. While our Ωm value is close to concordance, our σ8 value is ∼2σ higher because of the inflated observed number densities compared to theoretical mass function models owing to how our survey targeted overdense regions. With Euclid and several other large, unbiased optical surveys on the horizon, VMC mapping will enable optical/NIR cluster cosmology at redshifts much higher than what has been possible before.

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