Spatial Study with the Very Large Telescope of a New Resolved Edge-on Circumstellar Dust Disk Discovered at the Periphery of the ρ Ophiuchi Dark Cloud

N. Grosso, J. Alves, K. Wood, R. Neuhäuser, T. Montmerle, J. E. Bjorkman

We report the discovery in near-infrared (NIR) with SofI at the New

Technology Telescope (NTT) of a resolved circumstellar dust disk around

a 2MASS source at the periphery of the ρ Ophiuchi dark cloud. We

present follow-up observations in J, H, and Ks bands,

obtained with ISAAC at the Very Large Telescope (VLT) under 0.4" seeing

conditions, which unveil a dark dust lane oriented east-west between two

characteristic northern and southern reflection nebulae. This new

circumstellar dust disk has a radius of 2.15" (300 AU at 140 pc) and a

width of 1.2" (170 AU at 140 pc). Thanks to its location at the

periphery of the dense cores, it suffers small foreground visual

extinction (AV=2.1+/-2.6 mag). Although this disk is seen

close to edge-on, the two reflection nebulae display very different

colors. We introduce a new NIR data visualization called ``pixel NIR

color mapping'' (PICMap for short), which allows us to visualize

directly the NIR colors of the nebula pixels. Thanks to this method, we

identify a ridge, 0.3" (40 AU at 140 pc) to the north of the dark lane

and parallel to it, that displays an NIR color excess. This ridge

corresponds to an unusual increase of brightness from J to

Ks, which is also visible in the NTT observations obtained

130 days before the VLT ones. We also find that the northern nebula

shows ~3 mag more extinction than the southern nebula. We compute

axisymmetric disk models to reproduce the VLT scattered-light images and

the spectral energy distribution from optical to NIR. Our best model,

with a disk inclination i=86deg+/-1deg, correctly

reproduces the extension of the southern reflection nebula, but it is

not able to reproduce either the observed NIR color excess in the

northern nebula or the extinction difference between the two reflection

nebulae. We discuss the possible origin of the peculiar, asymmetrical

NIR color properties of this object.


Based on observations carried out at the European Southern Observatory,

La Silla, Chile, under project 67.C-0325(A), and at Paranal, Chile,

under service mode project 267.C-5699(A).

Department of Astrophysics
External organisation(s)
European Southern Observatory (Germany), Max-Planck-Institut für extraterrestrische Physik, Observatoire des sciences de l'univers de Grenoble, University of St. Andrews, French Alternative Energies and Atomic Energy Commission (CEA), University of Toledo
The Astrophysical Journal
Publication date
Peer reviewed
Austrian Fields of Science 2012
103004 Astrophysics
Portal url