J/AJ/148/11 Infrared photometry in Cygnus-X (Kryukova+, 2014)
The dependence of protostellar luminosity on environment in the Cygnus-X
star-forming complex.
Kryukova E., Megeath S.T., Hora J.L., Gutermuth R.A., Bontemps S.,
Kraemer K., Hennemann M., Schneider N., Smith H.A., Motte F.
<Astron. J., 148, 11 (2014)>
=2014AJ....148...11K 2014AJ....148...11K
ADC_Keywords: YSOs ; Photometry, infrared
Keywords: infrared: stars - stars: formation -
stars: luminosity function, mass function - stars: protostars
Abstract:
The Cygnus-X star-forming complex is one of the most active regions of
low- and high-mass star formation within 2kpc of the Sun. Using
mid-infrared photometry from the IRAC and MIPS Spitzer Cygnus-X Legacy
Survey, we have identified over 1800 protostar candidates. We compare
the protostellar luminosity functions of two regions within Cygnus-X:
CygX-South and CygX-North. These two clouds show distinctly different
morphologies suggestive of dissimilar star-forming environments. We
find the luminosity functions of these two regions are statistically
different. Furthermore, we compare the luminosity functions of
protostars found in regions of high and low stellar density within
Cygnus-X and find that the luminosity function in regions of high
stellar density is biased to higher luminosities. In total, these
observations provide further evidence that the luminosities of
protostars depend on their natal environment. We discuss the
implications this dependence has for the star formation process.
Description:
The Cygnus-X complex was the target of the Cygnus-X Spitzer Legacy
Survey (http://irsa.ipac.caltech.edu/data/SPITZER/Cygnus-X/), which
mapped 24deg2 of the complex with the IRAC and MIPS instruments on
board the Spitzer Space Telescope. We used IRAC aperture photometry
and MIPS 24µm point-spread function (PSF) photometry from Data
Release 1 Point Source Catalog.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 134 2007 Properties of protostar candidates in Cygnus-X
--------------------------------------------------------------------------------
See also:
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/144/31 : Spitzer+2MASS photometry of protostar candidates
(Kryukova+, 2012)
J/A+A/543/A101 : OB stars in Cygnus OB2 association (Comeron+, 2012)
J/ApJ/720/679 : Optical spectroscopy in Cygnus X region (Beerer+, 2010)
J/A+A/375/539 : JHK photometry of HII regions in Cyg X (Comeron+, 2001)
J/A+A/241/551 : Radio continuum in Cygnus X region (Wendker+ 1991)
http://irsa.ipac.caltech.edu/data/SPITZER/Cygnus-X/ : Cygnus-X Spitzer Legacy
Survey
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Hour of Right Ascension (J2000)
4- 5 I2 min RAm Minute of Right Ascension (J2000)
7- 11 F5.2 s RAs Second of Right Ascension (J2000)
13- 14 I2 deg DEd Degree of Declination (J2000)
16- 17 I2 arcmin DEm Arcminute of Declination (J2000)
19- 23 F5.2 arcsec DEs Arcsecond of Declination (J2000)
25- 29 F5.2 mag Jmag ? J band magnitude (1)
31- 34 F4.2 mag e_Jmag ? Uncertainty in Jmag
36- 40 F5.2 mag Hmag ? H band magnitude (1)
42- 45 F4.2 mag e_Hmag ? Uncertainty in Hmag
47- 51 F5.2 mag Ksmag ? Ks band magnitude (1)
53- 56 F4.2 mag e_Ksmag ? Uncertainty in Ksmag
58- 62 F5.2 mag [3.6] ? Spitzer/IRAC 3.6µm band magnitude
64- 67 F4.2 mag e_[3.6] ? Uncertainty in [3.6]
69- 73 F5.2 mag [4.5] ? Spitzer/IRAC 4.5µm band magnitude
75- 78 F4.2 mag e_[4.5] ? Uncertainty in [4.5]
80- 84 F5.2 mag [5.8] ? Spitzer/IRAC 5.8µm band magnitude
86- 89 F4.2 mag e_[5.8] ? Uncertainty in [5.8]
91- 95 F5.2 mag [8.0] ? Spitzer/IRAC 8.0µm band magnitude
97-100 F4.2 mag e_[8.0] ? Uncertainty in [8.0]
102-106 F5.2 mag [24] Spitzer/MIPS 24µm band magnitude
108-111 F4.2 mag e_[24] Uncertainty in 24mag
113-118 F6.3 --- alpha [-0.26/3.93] Spectral index α
120-127 F8.3 --- RMEDSQ [-100/224] Average RMEDSQ value Dc
within nn4 distance (4th nearest neighbor) (2)
129-134 F6.3 [Lsun] logL [-1/3.6] Log luminosity
--------------------------------------------------------------------------------
Note (1): Preferentially from the UKIDSS (Lucas et al. 2012, cat. II/316), but
for sources for which UKIDSS data do not exist, we use available photometry
from the 2MASS (cat. II/246).
Note (2): RMEDSQ is a measure of the fluctuations in the signal due to
nebulosity and neighboring point sources in an annulus immediately
surrounding a point source. Megeath et al. 2012 (J/AJ/144/192) define:
RMEDSQ=[median[(Sij-median(Sij))2]]1/2, where Sij is the signal
in DN/s/pix at a given pixel position (i,j). The median values are
determined for an annulus centered on each source; this annulus typically
extends from 6 to 11 pixels but is increased for more luminous sources.
We use the average RMEDSQ value of YSOs (protostar candidates projected
on AV>3 regions and Class II sources) within a critical distance,
Dc=0.62pc (see Section 3.2), of each protostar, which we denote
Dc value for that protostar. Using the mean RMEDSQ value for
nearby YSOs provides a more representative measurement of the typical
fluctuations in the regions surrounding each protostar than using only
the RMEDSQ value for the protostar.
To sort protostars by the local surface density of YSOs, we use the
nearest-neighbor distance. This distance is found to the fourth nearest
YSO, which we designate "nn4 distance" following the approach of
Kryukova et al. 2012 (cat. J/AJ/144/31). To determine if a protostar
candidate is in a high or low stellar density environment, we use the
median nn4 distance, denoted Dc (for critical distance), for the
Cygnus-X cloud nebulosity filtered sample.
The meaning of negative RMEDSQ values are not explained.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 13-Oct-2014