Identification of transitional disks in Chamaeleon withHerschel

Abstract

Context. Transitional disks are circumstellar disks with inner holes that in some cases are produced by planets and/or substellar companions in these systems. For this reason, these disks are extremely important for the study of planetary system formation. Aims. The Herschel Space Observatory provides an unique opportunity for studying the outer regions of protoplanetary disks. In this work we update previous knowledge on the transitional disks in the Chamaeleon I and II regions with data from the Herschel Gould Belt Survey. Methods. We propose a new method for transitional disk classification based on the WISE 12 µm − PACS 70 µm color, together with inspection of the Herschel images. We applied this method to the population of Class II sources in the Chamaeleon region and studied the spectral energy distributions of the transitional disks in the sample. We also built the median spectral energy distribution of Class II objects in these regions for comparison with transitional disks. Results. The proposed method allows a clear separation of the known transitional disks from the Class II sources. We find six transitional disks, all previously known, and identify five objects previously thought to be transitional as possibly non-transitional. We find higher fluxes at the PACS wavelengths in the sample of transitional disks than those of Class II objects. Conclusions. We show the Herschel 70 µm band to be a robust and efficient tool for transitional disk identification. The sensitivity and spatial resolution of Herschel reveals a significant contamination level among the previously identified transitional disk candidates for the two regions, which calls for a revision of previous samples of transitional disks in other regions. The systematic excess found at the PACS bands could be either a result of the mechanism that produces the transitional phase, or an indication of different evolutionary paths for transitional disks and Class II sources.

Infrared study of transitional disks in Ophiuchus withHerschel

“…All of these YSOs fell within the coverage of the maps used, and 49 were detected in at least one Herschel band, 49 in PACS, and 19 in SPIRE. This leads to a Herschel detection rate of 18.77%±2.6%, which is much smaller than the percentage of detections obtained in similar studies in Chamaeleon (Ribas et al 2013) and Lupus (Bustamante et al 2015) of around 30%. Given that Ophiuchus is closer than those regions (150 ∼ 200 pc), the low detection rate is probably due to the higher background, which is emitting at mid-and long-IR wavelengths, and precludes the detection of faint objects.…”

“…Seven of the detected objects were classified as transitional disk candidates by the criterion in Ribas et al (2013), and 11 more were classified according to the complementary criterion, generating a total sample of 18 transitional disk candidates. Some of these candidates were already imaged in previous works, and hence, confirmed.…”

“…In Sect. 3 we explain the results obtained from the data reduction, both with the method described in Ribas et al (2013) and with the analysis of the SED of each individual object. In Sect.…”

TheHerschelGould Belt Survey in Chamaeleon II

“…No color correction was applied. When no source was detected, we computed a flux upper limit (Table 3) as in Ribas et al (2013), i.e., calculating the rms of the sky emission over 100 apertures taken around the source, using the coordinates provided in Spezzi et al (2008) and the same aperture radii and correction factors as for detected sources.…”

“…The lists of point-like sources observed with the HGBS published so far are limited to previously confirmed YSOs (this work; Winston et al 2012;Ribas et al 2013), because the nature of the other detected sources needs further confirmation. Thus, there is no systematic study of the photometric completeness of the survey.…”