Sílvia Vicente1,2, I. Kamp1, O. Berné3, J. Champion3, W.-F. Thi4, P. Woitke5 1 Kapteyn Astronomical Institute, Univ. of Groningen, 2 IA, Lisbon, Portugal, 3UPS-OMP, IRAP, Toulouse, France

4 IMPE, Garching, Germany, 5 University of St-Andrews , Scotland

vicente@astro.rug.nl

Motivation

Herschel Results Champion +2015, in prep.

ProDiMo model Vicente +2015, in prep. ProDiMo, a thermo-chemical model for protoplanetary disks (Woitke+2009, Kamp+2010, Thi+2011) was used to interpret the VLT and Herschel observations of HST10. The code provides as output the chemical abundances, disk radial profiles, the dominant heating and cooling mechanisms, and emission line profiles. The external environment of HST10 was simulated with two disk halves cut along the disk midplane. The upper-half was exposed to a strong FUV field while the lower-half to a typical ISM UV field. The input model parameters are in the table aside. The external irradiated disk shows stronger line fluxes in H2 2.12, [OI]63, [CII]157 (line profiles on the right) and CO, which makes them good tracer species for proplyd disk structure and composition.

PAHs (VLT/VISIR) and H2 (AO images) Vicente +2013

The 3 proplyds were observed with PACS and HIFI as part of the open time key program “A Herschel survey of PDRs in proplyds” (PI, O. Berné). [CII]157 was detected with HIFI in all 3 objects. The Carina candidate shows emission in all lines with exception of CO(17-16). The Orion proplyds (10x smaller) show no other detections due to beam dilution and large contamination from the nebula. A program (PI, S. Vicente) with SOFIA/GREAT is being conducted to spectrally resolve the [OI]63 line in the 3 objects.

The Meudon PDR code (Le Petit+2006) was used to interpret the results for the Carina candidate. Two components with constant density could reproduce all the observed line fluxes. [CII]157 and [OII]63 are reproduced by an envelope of 104 cm-3, while CO emission comes mostly from a compact 106 cm-3

region inside the envelope (see plot on the right).

Proplyds are young stellar objects (YSOs) surrounded by Solar System-sized protoplanetary disks and found embedded within or near a HII region. Their typical teardrop shaped ionized cocoons originate from the photoevaporation of the disk/envelope by the external UV radiation from nearby OB stars. The photo-evaporation wind results from the formation of a high-density (~106 cm-3) photo-dissociation region or PDR (Fig.1) at the surface of the disk where FUV photons heat the gas. The cooling occurs by the emission of far-IR lines of atomic and molecular species such as [OI], [CII] and high-J CO. The heating and cooling mechanisms at work at the disk surface will determine the photoevaporation rate, the proplyd morphology observed in the different species, and the lifetime of the gaseous disk, constraining also the formation of giant planets.

Here we report the observational and modeling results for our 3 best studied objects, the proplyds HST10 and 244-440, located in the Orion Nebula (d= 414pc), and a proplyd candidate in the Carina Nebula (d= 2.3 kpc).

References Bally, O’Dell & McCaughrean 2000, AJ, 119, 2919 Jonhstone, Hollenbach & Bally 1998, ApJ, 499, 758 Gorti & Hollenbach 2009, ApJ, 690, 1539 Henney & O’Dell 1999, AJ, 118, 2350 Kamp, Tilling, Woitke et al. 2010, A&A, 510, 18

Figure 1: PDR structure in proplyds (Richling & Yorke 2000)

[CII]157 FUV = G0 FUV = 105 G0

Le Petit et al. 2006, ApJS, 164, 506 O’Dell, Wen & Wu 1993, ApJ, 410, 696 Richling & Yorke 2000, A&A, 340, 508 Smith et al. 2003, ApJL, 587, 105 Störzer & Hollenbach 1999, ApJ, 515, 669

Thi, Woitke & Kamp 2011, MNRAS, 412, 711 Vicente & Alves 2005, A&A, 441, 195 Vicente, PhD Thesis 2009 Vicente et al. 2013, ApJL, 765, 38V Woitke, Kamp & Thi 2009, A&A, 501, 383

S. Vicente

~ 106 cm-3

PDR

fCPAHs (PDR) = 8.0 x 10-4 …or 50x less than the ISM! Photoelectric heating reduced!

Vicente et al. (2013)

HST10_lower HST10_upper