Spitzer observations of NGC 2264: the nature of the disk population

Author(s)

P. S. Teixeira, C. J. Lada, M. Marengo, E. A. Lada

Abstract

Aims: NGC 2264 is a young cluster with a rich circumstellar disk

population which makes it an ideal target for studying the evolution of

stellar clusters. Our goal is to study the star formation history of NGC

2264 and to analyse the primordial disk evolution of its members.

Methods: The study presented is based on data obtained with the Infrared

Array Camera (IRAC) and the Multiband Imaging Photometer for Spitzer

(MIPS) on board the Spitzer Space Telescope, combined with deep

near-infrared (NIR) ground-based FLAMINGOS imaging and previously

published optical data. Results: We build NIR dust extinction

maps of the molecular cloud associated with the cluster, and determine

it to have a mass of 2.1 × 103 M⊙ above

an AV of 7 mag. Using a differential Ks-band

luminosity function (KLF) of the cluster, we estimate the size of the

population of NGC 2264, within the area observed by FLAMINGOS, to be

1436 ± 242 members. The star formation efficiency is ≥ ~25%.

We identify the disk population and divide it into 3 groups based on

their spectral energy distribution slopes from 3.6 μm to 8 μm and

on the 24 μm excess emission: (i) optically thick inner disks, (ii)

anaemic inner disks, and (iii) disks with inner holes, or transition

disks. We analyse the spatial distribution of these sources and find

that sources with thick disks segregate into sub-clusterings, whereas

sources with anaemic disks do not. Furthermore, sources with anaemic

disks are found to be unembedded (i.e., with AV <3 mag),

whereas the clustered sources with thick disks are still embedded within

the parental cloud. Conclusions: NGC 2264 has undergone more than

one star-forming event, where the anaemic and extincted thick disk

population appear to have formed in separate episodes: the sources with

anaemic disks are more evolved and have had time to disperse and

populate a halo of the cluster. We also find tentative evidence of

triggered star-formation in the Fox Fur Nebula. In terms of disk

evolution, our findings support the emerging disk evolution paradigm of

two distinct evolutionary paths for primordial optically thick disks: a

homologous one where the disk emission decreases uniformly at NIR and

mid-infrared (MIR) wavelengths, and a radially differential one where

the emission from the inner region of the disk decreases more rapidly

than from the outer region (forming transition disks).

Organisation(s)

Department of Astrophysics

External organisation(s)

Harvard-Smithsonian Center for Astrophysics, Iowa State University, University of Florida, Gainesville, European Southern Observatory (Germany)

Journal

Astronomy & Astrophysics

Volume

540

No. of pages

13

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201015326

Publication date

04-2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics, 103003 Astronomy

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/1f1c2707-812e-4b1f-978f-dffd161212e0