Aims. We study the dependence of protoplanetary disk evolution on stellar mass using a large sample of young stellar objects in nearby young star-forming regions. Methods. We update the ...protoplanetary disk fractions presented in our recent work (Paper I of this series) derived for 22 nearby (<500 pc) associations between 1 and 100 Myr. We use a subsample of 1428 spectroscopically confirmed members to study the impact of stellar mass on protoplanetary disk evolution. We divide this sample into two stellar mass bins (2 M⊙ boundary) and two age bins (3 Myr boundary), and use infrared excesses over the photospheric emission to classify objects in three groups: protoplanetary disks, evolved disks, and diskless. The homogeneous analysis and bias corrections allow for a statistically significant inter-comparison of the obtained results. Results. We find robust statistical evidence of disk evolution dependence with stellar mass. Our results, combined with previous studies on disk evolution, confirm that protoplanetary disks evolve faster and/or earlier around high-mass (>2 M⊙) stars. We also find a roughly constant level of evolved disks throughout the whole age and stellar mass spectra. Conclusions. We conclude that protoplanetary disk evolution depends on stellar mass. Such a dependence could have important implications for gas giant planet formation and migration, and could contribute to explaining the apparent paucity of hot Jupiters around high-mass stars.
We present high-resolution, high dynamic range column-density and color-temperature maps of the Orion complex using a combination of Planck dust-emission maps, Herschel dust-emission maps, and 2MASS ...NIR dust-extinction maps. The column-density maps combine the robustness of the 2MASS NIR extinction maps with the resolution and coverage of the Herschel and Planck dust-emission maps and constitute the highest dynamic range column-density maps ever constructed for the entire Orion complex, covering 0.01 mag < A sub(K) < 30 mag, or 2 x 10 super(20) cm-2 < N < 2 x 10 super(23) cm-2. We determined the ratio of the 2.2 mu m extinction coefficient to the 850 mu m opacity and found that the values obtained for both Orion A and B are significantly lower than the predictions of standard dust models, but agree with newer models that incorporate icy silicate-graphite conglomerates for the grain population. We show that the cloud projected probability distribution function, over a large range of column densities, can be well fitted by a simple power law. Moreover, we considered the local Schmidt-law for star formation, and confirm earlier results, showing that the protostar surface density capital sigma * follows a simple law capital sigma * proportional, variant capital sigma sub(gas) super( beta ) with beta ~2.
We study the evolution of circumstellar disks in 22 young nearby associations over the entire mass spectrum using photometry covering from the optical to the mid-infrared. We compiled a catalog of ...2340 spectroscopically-confirmed members of these nearby associations. We analyzed their spectral energy distributions and searched for excess related to the presence of protoplanetary disks. The dataset has been analyzed in a homogeneous and consistent way, allowing for meaningful inter-comparison of results obtained for individual regions. The increase in timescale of excess decay at longer wavelength is compatible with inside-out disk clearing scenarios. The increased timescale of decay and larger dispersion in the distribution of disk fractions at 22-24 mu m suggest that the inner and outer zones evolve differently, the latter potentially following a variety of evolutionary paths. The drop of primordial disks and the coincident rise of evolved disks at 10 Myr are compatible with planet formation theories suggesting that the disappearance of the gas is immediately followed by the dynamical stirring of the disk.
Abstract
Far-infrared and (sub)millimeter fluxes can be used to study dust in protoplanetary disks, the building blocks of planets. Here, we combine observations from the
Herschel Space Observatory
...with ancillary data of 284 protoplanetary disks in the Taurus, Chamaeleon I, and Ophiuchus star-forming regions, covering from the optical to mm/cm wavelengths. We analyze their spectral indices as a function of wavelength and determine their (sub)millimeter slopes when possible. Most disks display observational evidence of grain growth, in agreement with previous studies. No correlation is found between other tracers of disk evolution and the millimeter spectral indices. A simple disk model is used to fit these sources, and we derive posterior distributions for the optical depth at 1.3 mm and 10 au, the disk temperature at this same radius, and the dust opacity spectral index
β
. We find the fluxes at 70
μ
m to correlate strongly with disk temperatures at 10 au, as derived from these simple models. We find tentative evidence for spectral indices in Chamaeleon I being steeper than those of disks in Taurus/Ophiuchus, although more millimeter observations are needed to confirm this trend and identify its possible origin. Additionally, we determine the median spectral energy distribution of each region and find them to be similar across the entire wavelength range studied, possibly due to the large scatter in disk properties and morphologies.
We present optical depth and temperature maps of the Perseus molecular cloud, obtained combining dust emission data from the Herschel and Planck satellites and 2MASS/NIR dust extinction maps. The ...maps have a resolution of 36 arcsec in the Herschel regions, and of 5 arcmin elsewhere. The dynamic range of the optical depth map ranges from 1 x 10 super(-2) mag up to 20 mag in the equivalent K-band extinction. We also evaluate the ratio between the 2.2 mu m extinction coefficient and the 850 mu m opacity. The value we obtain is close to the one found in the Orion B molecular cloud. We show that the cumulative and the differential area function of the data (which is proportional to the probability distribution function of the cloud column density) follow power laws with an index of respectively =-2, and =-3. We use WISE data to improve current YSO catalogs based mostly on Spitzer data and we build an up-to-date selection of Class I/0 objects. Using this selection, we evaluate the local Schmidt law, capital sigma sub(YSO)is proportional to capital sigma sub(gas) super( beta ), showing that beta = 2.4 + or - 0.6. Finally, we show that the area-extinction relation is important for determining the star-formation rate in the cloud, which is in agreement with other recent works.
3D shape of Orion A from Gaia DR2 Großschedl, Josefa E.; Alves, João; Meingast, Stefan ...
Astronomy and astrophysics (Berlin),
11/2018, Letnik:
619
Journal Article
Recenzirano
Odprti dostop
We use the Gaia DR2 distances of about 700 mid-infrared selected young stellar objects in the benchmark giant molecular cloud Orion A to infer its 3D shape and orientation. We find that Orion A is ...not the fairly straight filamentary cloud that we see in (2D) projection, but instead a cometary-like cloud oriented toward the Galactic plane, with two distinct components: a denser and enhanced star-forming (bent) Head, and a lower density and star-formation quieter ∼75 pc long Tail. The true extent of Orion A is not the projected ∼40 pc but ∼90 pc, making it by far the largest molecular cloud in the local neighborhood. Its aspect ratio (∼30:1) and high column-density fraction (∼45%) make it similar to large-scale Milky Way filaments (“bones”), despite its distance to the galactic mid-plane being an order of magnitude larger than typically found for these structures.
VISIONS: the VISTA Star Formation Atlas Meingast, Stefan; Bouy, Hervé; Fürnkranz, Verena ...
Astronomy and astrophysics (Berlin),
05/2023, Letnik:
673
Journal Article
Recenzirano
Odprti dostop
The VISIONS public survey provides large-scale, multi-epoch imaging of five nearby star-forming regions at sub-arcsecond resolution in the near-infrared. All data collected within the program and ...provided by the European Southern Observatory (ESO) science archive are processed with a custom end-to-end pipeline infrastructure to provide science-ready images and source catalogs. The data reduction environment has been specifically developed for the purpose of mitigating several shortcomings of the bona fide data products processed with software provided by the Cambridge Astronomical Survey Unit (CASU), such as spatially variable astrometric and photometric biases of up to 100 mas and 0.1 mag, respectively. At the same time, the resolution of co-added images is up to 20% higher compared to the same products from the CASU processing environment. Most pipeline modules are written in Python and make extensive use of C extension libraries for numeric computations, thereby simultaneously providing accessibility, robustness, and high performance. The astrometric calibration is performed relative to the
Gaia
reference frame, and fluxes are calibrated with respect to the source magnitudes provided in the Two Micron All Sky Survey (2MASS). For bright sources, absolute astrometric errors are typically on the order of 10–15 mas and fluxes are determined with sub-percent precision. Moreover, the calibration with respect to 2MASS photometry is largely free of color terms. The pipeline produces data that are compliant with the ESO Phase 3 regulations and furthermore provides curated source catalogs that are structured similarly to those provided by the 2MASS survey.
Abstract
The recently rediscovered open cluster Stock 2, located roughly 375 pc away and about 400 Myr old, has the potential to be an exciting new testbed for our understanding of stellar evolution. ...We present results from a spectroscopic campaign to characterize stars near the cluster’s main-sequence turnoff; our goal is to identify candidate chemically peculiar stars among the cluster’s A stars. We obtained échelle spectra for 64 cluster members with ESPaDOnS on the 3.6 m Canada–France–Hawaii Telescope, Maunakea Observatory, USA, and for six stars with SOPHIE on the 1.93 m telescope at the Observatoire de Haute-Provence, France. We complemented these new observations with those of 13 high-mass cluster members from the HARPS-N archive; our overall sample is of 71 stars. We derived the fundamental parameters (
T
eff
,
log
g
, M/H) as well as
v
e
sin
i
for our sample using the sliced inverse regression technique, and then used
iSpec
to derive individual abundances of 12 chemical species. With these abundance determinations, we identified nine A stars with anomalous levels of Sc, Ca, and other metallic lines. Follow-up observations of these Am candidates with a known age can transform them into benchmarks for evolutionary models that include atomic diffusion and help build a better understanding of the complex interactions between macroscopic and microscopic processes in stellar interiors.
ABSTRACT We introduce a novel technique to mitigate the adverse effects of atmospheric turbulence on astronomical imaging. Utilizing a video-to-image neural network trained on simulated data, our ...method processes a sliding sequence of short-exposure (∼0.2 s) stellar field images to reconstruct an image devoid of both turbulence and noise. We demonstrate the method with simulated and observed stellar fields, and show that the brief exposure sequence allows the network to accurately associate speckles to their originating stars and effectively disentangle light from adjacent sources across a range of seeing conditions, all while preserving flux to a lower signal-to-noise ratio than an average stack. This approach results in a marked improvement in angular resolution without compromising the astrometric stability of the final image.
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