# Characterization of proplyds in Orion

Coordinator: N. Hu'elamo, M.F. Sterzik, C. Melo, S. Vicente, A. Muench, J. Alves

Abstract:
Planetary systems are supposed to form in dusty circumstellar disks, although dust properties (size, temperature, distribution) and dust evolution are still not well understood. The Orion star forming region (SFR) is an ideal laboratory to test planetary theories, given that it contains a large number of low-mass stars surrounded by dusty envelopes, disks and tails, the so-called 'proplyds' (e.g. O'Dell \& Wen 1994, Bally et al. 2000). Proplyds are suitable targets to characterize protoplanetary disks at early evolutioanry stages. They have been resolved at optical and near-infrared wavelengths and those observations have provided important information about their hot dust content. We propose for VLT/VISIR observations to characterize their warm dust content, composition and morphology. We have selected four fields in the Orion SFR which contain proplyds with different properties (see Table~1). Some of the targets have been previously detected at 10\,$\mu$m with 3m and 5m-class telescopes (e.g. Robberto et al. 1999, Hayward \& McCaughrean 1997). We will take advantage of the unprecedented spatial resolution of VLT/VISIR to resolve the proposed targets. Imaging observations in the N-band will allow to characterize the dust around the central sources. We will probe the silicate feature at 9.7 $\mu$m observing the targets in three different filters (PAH1, PAH2 and SIV). The comparison of the derived fluxes with dust emission models will provide information about grain sizes. Low resolution spectroscopy of the brightest sources will allow to study dust composition in more detail. According to previous observations, we expect N-band fluxes between 10-100\,mJy (Hayward \& McCaughcrean 1997, Robberto et al. 2002). Assuming a sensitivity of 8mJy/1hr/10$\sigma$, we have estimated a total of 5 hours (including overheads) to image the four fields in two N-band filters. We have estimated 3 hours to carry out spectrocopy of the brightest sources, that is, we require 8 hours to complete the study.

Project description/science scope

Data:

Observing strategy

IMAGING Observations

We will use classical chopping/nodding techniques to observe the three selected fields in three filters: PAH1, PAH2 and SIV. We will use AutoChopNod templates. The three fields will be observed at two different chopping angles: the idea is to have different sky subtractions to better trace the emission from the nebula.

SPECTROSCOPIC observations

We will observe a total of five proplyds with the spectrometer. Two proplyds (170-337 and 159-350) are double, so we will place both the proplyd and the companion within the slit. We have include a rotator angle in the OBs with this purpose. We plan to take LR spectra. Central wavelength: 9.8 microns. Slit width: 0.75 arcsec We plan to nod on the slit with chop throws of 10''.

 Name RA(2000) DEC(2000) Mode Obs.Time (h) Priority 170-337 + 05 35 17.3 -05 23 38.9 IMG/PAH1/PAH2/SIV 3 1 171-340 + . . . 1 1 177-341^1 . . . 1 1 159-350 + 160-353 05 35 15.9 -05 23 50.0 IMG/PAH1/PAH2/SIV 1:00h 2 218-354 05 35 21.79 -05 23 53.9 IMG/PAH1/PAH2/SIV 1 3 170-337+171-340 05 35 16.9 -05 23 37.0 SPEC/LR/9.8/0.75"slit 1 4 177-341 05 35 17.67 -05 23 40.9 " 1 5 159-350+160-353 05 35 15.9 -05 23 50.0 " 1 6

Notes: Approved time: 5h (imaging) / 3h (spectroscopy)
Time critical: all our targets are in Orion, so they are observable between nov-jan.

^1 the 3 targets fit on VISIR FOV of 19.2"x19.2"