Examinando por Autor "Caceres C."

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    ALMA survey of circumstellar discs in the young stellar cluster IC 348
    (Oxford University Press, 2018-08) Ruĭz-Rodrĭguez D.; Cieza L.A.; Williams J.P.; Andrews S.M.; Principe D.A.; Caceres C.; Canovas H.; Casassus S.; Schreiber M.R.; Kastner J.H.
    We present a 1.3 mm continuum survey of the young (2-3 Myr) stellar cluster IC 348 that lies at a distance of 310 pc and is dominated by low-mass stars (M(star operator) ~ 0.1-0.6 M⊙). We observed 136 Class II sources (discs that are optically thick in the infrared) at 0.8 arcsec (200 au) resolution with a 3σ sensitivity of ~ 0.45 mJy (Mdust ~1.3M⊕).We detect 40 of the targets and construct a mm-continuum luminosity function.We compare the disc mass distribution in IC 348 to those of younger and older regions, taking into account the dependence on stellar mass. We find a clear evolution in disc masses from 1 to 5-10 Myr. The disc masses in IC 348 are significantly lower than those in Taurus (1-3 Myr) and Lupus (1-3 Myr), similar to those of Chamaleon I, (2-3 Myr) and s Ori (3-5 Myr) and significantly higher than in Upper Scorpiusrpius (5-10 Myr). About 20 discs in our sample (5 per cent of the cluster members) have estimated masses (dust + gas) > 1MJup and hence might be the precursors of giant planets in the cluster. Some of the most massive discs include transition objects with inner opacity holes based on their infrared Spectral Energy Distribution (SEDs). From a stacking analysis of the 96 non-detections, we find that these discs have a typical dust mass of just ≲ 0.4 M⊕, even though the vast majority of their infrared SEDs remain optically thick and show little signs of evolution. Such low-mass discs may be the precursors of the small rocky planets found by Kepler around M-type stars. © 2018 The Author(s).
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    Constraining the mass of the planet(s) sculpting a disk cavity: The intriguing case of 2MASS J16042165-2130284
    (EDP Sciences, 2017-02) Canovas H.; Hardy A.; Zurlo A.; Wahhaj Z.; Schreiber M.R.; Vigan A.; Villaver E.; Olofsson J.; Meeus G.; Ménard F.; Caceres C.; Cieza L.A.; Garufi A.
    Context. The large cavities observed in the dust and gas distributions of transition disks may be explained by planet-disk interactions. At ∼ 145 pc, 2MASS J16042165-2130284 (J1604) is a 5-12 Myr old transitional disk with different gap sizes in the mm- and μm-sized dust distributions (outer edges at ∼ 79 and at ∼ 63 au, respectively). Its 12CO emission shows a ∼ 30 au cavity. This radial structure suggests that giant planets are sculpting this disk. Aims. We aim to constrain the masses and locations of plausible giant planets around J1604. Methods. We observed J1604 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) at the Very Large Telescope (VLT), in IRDIFS-EXT, pupil-stabilized mode, obtaining YJH-band images with the integral field spectrograph (IFS) and K1K2-band images with the Infra-Red Dual-beam Imager and Spectrograph (IRDIS). The dataset was processed exploiting the angular differential imaging (ADI) technique with high-contrast algorithms. Results. Our observations reach a contrast of ΔK,ΔYH ∼ 12 mag from 0″.15 to 0″.80 (∼ 22 to 115 au), but no planet candidate is detected. The disk is directly imaged in scattered light at all bands from Y to K, and it shows a red color. This indicates that the dust particles in the disk surface are mainly ≥ 0.3 μm-sized grains. We confirm the sharp dip/decrement in scattered light in agreement with polarized light observations. Comparing our images with a radiative transfer model we argue that the southern side of the disk is most likely the nearest. Conclusions. This work represents the deepest search yet for companions around J1604. We reach a mass sensitivity of ≥ 2-3 MJup from ∼ 22 to ∼ 115 au according to a hot start scenario. We propose that a brown dwarf orbiting inside of ∼ 15 au and additional Jovian planets at larger radii could account for the observed properties of J1604 while explaining our lack of detection. © ESO, 2017.
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    DZ Chamaeleontis: A bona fide photoevaporating disc
    (EDP Sciences, 2018-02) Canovas H.; Montesinos B.; Schreiber M.R.; Cieza L.A.; Eiroa C.; Meeus G.; De Boer J.; Ménard F.; Wahhaj Z.; Riviere-Marichalar P.; Olofsson J.; Garufi A.; Rebollido I.; Van Holstein R.G.; Caceres C.; Hardy A.; Villaver E.
    Context. DZ Cha is a weak-lined T Tauri star (WTTS) surrounded by a bright protoplanetary disc with evidence of inner disc clearing. Its narrow Hα line and infrared spectral energy distribution suggest that DZ Cha may be a photoevaporating disc. Aims. We aim to analyse the DZ Cha star + disc system to identify the mechanism driving the evolution of this object. Methods. We have analysed three epochs of high resolution optical spectroscopy, photometry from the UV up to the sub-mm regime, infrared spectroscopy, and J-band imaging polarimetry observations of DZ Cha. Results. Combining our analysis with previous studies we find no signatures of accretion in the Hα line profile in nine epochs covering a time baseline of ∼20 yr. The optical spectra are dominated by chromospheric emission lines, but they also show emission from the forbidden lines [SII] 4068 and [OI] 6300Å that indicate a disc outflow. The polarized images reveal a dust depleted cavity of ∼7 au in radius and two spiral-like features, and we derive a disc dust mass limit of Mdust< 3 MEarth from the sub-mm photometry. No stellar (M∗> 80 MJup) companions are detected down to 0″.07 (∼8 au, projected). Conclusions. The negligible accretion rate, small cavity, and forbidden line emission strongly suggests that DZ Cha is currently at the initial stages of disc clearing by photoevaporation. At this point the inner disc has drained and the inner wall of the truncated outer disc is directly exposed to the stellar radiation. We argue that other mechanisms like planet formation or binarity cannot explain the observed properties of DZ Cha. The scarcity of objects like this one is in line with the dispersal timescale (≲105 yr) predicted by this theory. DZ Cha is therefore an ideal target to study the initial stages of photoevaporation. © ESO, 2018.