J/A+A/621/A14 Blind photometric study of NGC 2264 region (Venuti+, 2019)
Deep, multi-band photometry of low-mass stars to reveal young clusters:
A blind study of the NGC 2264 region.
Venuti L., Damiani F., Prisinzano L.
<Astron. Astrophys. 621, A14 (2019)>
=2019A&A...621A..14V 2019A&A...621A..14V (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open; Colors; Photometry; Stars, M-type;
Stars, pre-main sequence; YSOs
Keywords: methods: observational - techniques: photometric -
methods: statistical - surveys - stars: low-mass -
open clusters and associations: individual: NGC 2264
Abstract:
Thanks to their extensive and homogeneous sky coverage, deep,
large-scale, multi-wavelength surveys are uniquely suited to
statistically identify and map young star clusters in our Galaxy. Such
studies are crucial to address themes like the initial mass function,
or the modes and dynamics of star cluster formation and evolution.
We aim to test a purely photometric approach to statistically identify
a young clustered population embedded in a large population of field
stars, with no prior knowledge on the nature of stars in the field. We
conducted our blind test study on the NGC 2264 region, which hosts a
well-known, richly populated young cluster (∼3Myr-old) and several
active star-forming sites.
We selected a large (4 deg2) area around the NGC 2264 cluster, and
assembled an extensive r, i, J catalog of the field from pre-existing
large-scale surveys, notably Pan-STARRS1 and UKIDSS. We then mapped
the stellar color locus on the (i-J, r-i) diagram to select M-type
stars, which offer the following observational advantages with respect
to more massive stars: i) they comprise a significant fraction of the
Galactic stellar population; ii) their pre-main sequence phase lasts
significantly longer than for higher-mass stars; iii) they exhibit the
strongest luminosity evolution from the pre-main sequence to the main
sequence; iv) their observed r, i, J colors provide a direct and
empirical estimate of AV. A comparative analysis of the photometric
and spatial properties of M-type stars as a function of AV enabled us
to probe the structure and stellar content of our field.
Using only r, i, J photometry, we could identify two distinct
populations in our field: a diffuse field population and a clustered
population in the center of the field. The presence of a concentration
of occulting material, spatially associated with the clustered
population, allowed us to derive an estimate of its distance
(800-900pc) and age (0.5-5Myr); these values are overall
consistent with the literature parameters for the NGC 2264
star-forming region. The extracted clustered population exhibits a
hierarchical structure, with two main clumps and peaks in number
density of objects around the most extincted locations within the
field. An excellent agreement is found between the observed
substructures for the clustered population and a map of the NGC 2264
subregions reported in the literature. Our selection of clustered
members is coherent with the literature census of the NGC 2264 cluster
for about 95% of the objects located in the inner regions of the
field, where the estimated contamination rate by field stars in our
sample is only 2%. In addition, the availability of a uniform dataset
for a large area around the NGC 2264 region enabled us to discover a
population of about a hundred stars with indications of statistical
membership to the cluster, therefore extending the low-mass population
census of NGC 2264 to distances of 10-15pc from the cluster cores.
By making use solely of deep, multi-band (r, i, J) photometry, without
assuming any further knowledge on the stellar population of our field,
we were able to statistically identify and reconstruct the structure
of a very young cluster that has been a prime target for star
formation studies over several decades. The method tested here can be
readily applied to surveys such as Pan-STARRS and the future LSST to
undertake a first complete census of low-mass, young stellar
populations down to distances of several kpc across the Galactic
plane.
Description:
We aim to test a purely photometric approach to statistically identify
a young clustered population embedded in a large population of field
stars, with no prior knowledge on the nature of stars in the field. We
conducted our blind test study on a large (4 sq. deg.) field around
the NGC 2264 cluster, making use of r,i,J photometry from existing
large-scale surveys. We focused on the M-type population of the field,
which exhibits the most favorable PMS/MS luminosity contrast, and for
which a direct and empirical estimate of individual Av can be derived
from r,i,J colors. We then conducted a comparative analysis of the
photometric and spatial properties of M-type stars as a function of Av
to probe the structure and stellar content of our field.
In table4, we list the M-type stars that we selected statistically as
part of the young clustered population embedded in the NGC 2264 field.
For each star, we provide the following information: object
coordinates (RA, Dec); r,i,J photometry and associated
uncertainties; name of the catalogs/surveys from which the listed
optical (r,i) and NIR (J) photometry were extracted; measured Av;
object identifier in the CSI 2264 campaign on the NGC 2264 region;
membership classification in the CSI 2264 catalog.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 100 1369 List of the M-type clustered population
identified in the NGC 2264 field
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/321 : IPHAS DR2 Source Catalogue (Barentsen+, 2014)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/A+A/570/A82 : Mapping accretion variability in NGC 2264 (Venuti+, 2014)
J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right ascension (J2000)
11- 18 F8.5 deg DEdeg Declination (J2000)
20- 25 F6.3 mag rmag r-band photometry
27- 32 F6.3 mag imag i-band photometry
34- 39 F6.3 mag Jmag J-band photometry
41- 45 F5.3 mag e_rmag r-band photometry uncertainty
47- 51 F5.3 mag e_imag i-band photometry uncertainty
53- 57 F5.3 mag e_Jmag J-band photometry uncertainty
59- 69 A11 --- r_rmag Survey of reference for (r,i) photometry
(CSI2264, IPHAS, Pan-STARRS1 or SDSS)
71- 76 A6 --- r_Jmag Survey of reference for J-band photometry
(2MASS or UKIDSS)
78- 83 F6.3 mag AV Measured individual Av
85- 97 A13 --- CSIMON Object identifier in the CSI 2264 catalog,
CSIMon-NNNNNN
99-100 I2 --- Memb [-1/2]? Membership flag in the
CSI 2264 catalog (1)
--------------------------------------------------------------------------------
Note (1): Membership flag as follows:
1 = very likely NGC 2264 member
2 = possible NGC 2264 member
-1 = likely field object
0 = no membership information
--------------------------------------------------------------------------------
Acknowledgements:
Laura Venuti, lvenuti27(at)gmail.com
(End) Laura Venuti [INAF-OAPa, Italy], Patricia Vannier [CDS] 14-Nov-2018