J/A+A/527/A62 HK photometry in an UCHII region near Sh2-217 (Brand+, 2011)
Triggered star formation at the borders of the HII region Sh 2-217.
Brand J., Massi F., Zavagno A., Deharveng L., Lefloch B.
<Astron. Astrophys. 527, A62 (2011)>
=2011A&A...527A..62B 2011A&A...527A..62B
ADC_Keywords: H II regions; Stars, normal; Photometry, CCD; Photometry, infrared
Keywords: stars: formation - ISM: clouds - ISM: individual objects: Sh 2-217
Abstract:
We study stars and gas in and around the HII region Sh 2-217 to see if
the various physical parameters derived from the data (such as column
densities, masses, sizes, and timescales) are consistent with the
predictions of a simple model of the collect-and-collapse mechanism.
This should indicate whether stars forming in molecular gas at the
borders of the HII region could have been triggered by the expansion
of the ionized gas.
We observed the emission of various molecules and transitions towards
Sh 2-217, and obtained both near-infrared photometry in the H and K
bands, and near-infrared images in [FeII] and H2 narrow-band filters
of the stars in a molecular condensation at the edge of the HII
region, where an UC HII region is also located.
Description:
Coordinates and photometric parameters (magnitudes and colours) are
presented of the stars located in a molecular condensation on the
SW-border of the Galactic HII region Sh2-217. The data were obtained
on January 4, 2004 with the 3.58-m Telescopio Nazionale Galileo (TNG;
La Palma, Canary Islands, Spain). Near-infrared observations were
carried out through H and K' broad-band filters with the camera NICS.
The image scale is 0.25arcsec/pixel, yielding a field of view of
about 4.2'x4.2'. Observing strategy and exposure times are described
in Deharveng et al. (2006A&A...458..191D 2006A&A...458..191D), the only difference being
that the dithering sequence for the H-band images was the same as
adopted for K'. The data reduction steps adopted are outlined in
Deharveng et al. (2006A&A...458..191D 2006A&A...458..191D). Aperture photometry was done
using the DAOPHOT package in IRAF. We followed the same procedure
described in Deharveng et al. (2006A&A...458..191D 2006A&A...458..191D) to obtain aperture
photometry, after which PSF-fitting photometry was performed.
Although the seeing was good (<1"), the night was barely photometric,
so we calibrated our H, K' photometry with that performed on the same
field by Deharveng et al. (2003, Cat. J/A+A/399/1135). We calculated
the difference in magnitudes for each coinciding source and plotted it
against our derived instrumental H-K'. A colour term was present in
K' because of the difference between the K and K' filters. After a
best-fit calibration, a residual r.m.s. of about 0.2mag. was present
in the difference between our photometry and that of Deharveng et al.
(2003, J/A+A/399/1135), probably because of the different seeing and
possibly also due to the intrinsic variability of young stars. Our
photometry is thus on the same HK standard system as Deharveng et al.
(2003, J/A+A/399/1135). Sources with K, H < 11-12 are in the
non-linear regime or saturated, but such bright objects are few in
number and lie outside the cluster, and are probably foreground stars.
The approximate limiting magnitudes are K=18.48 and H=19.52, much
deeper than achieved by Deharveng et al. (2003, J/A+A/399/1135). We
estimate completeness limits of approximately K=16.5 and H=17.5 from
the peak in histograms of the number of detected sources as a function
of magnitude, after binning in 1mag. intervals.
The astrometric calibration of the frames was obtained by measuring
the position on the image of a sample of stars and fitting those
positions to the equatorial coordinates given by Deharveng et al.
(2006A&A...458..191D 2006A&A...458..191D), using tasks of STSDAS/IRAF. The typical
accuracy of this procedure is of the order of 1".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 66 812 Coordinates, magnitudes, and colours for 812
stars in an UCHII region near Sh 2-217
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See also:
J/A+A/399/1135 : JHK photometry around Sh 217 and Sh 219 (Deharveng+, 2003)
Byte-by-byte Description of file:table7.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right Ascension J2000 (hours)
4- 5 I2 min RAm Right Ascension J2000 (minutes)
7- 11 F5.2 s RAs Right Ascension J2000 (seconds)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination J2000 (degrees)
17- 18 I2 arcmin DEm Declination J2000 (minutes)
20- 24 F5.2 arcsec DEs Declination J2000 (seconds)
26 A1 -- l_Kmag [>] indicates lower limit K-band magnitude
(records 669 to 812 only) (1)
27- 32 F6.3 mag Kmag TNG/NICS K'-band (2.2um) magnitude
34- 38 F5.3 mag e_Kmag ? Uncertainty in K-band magnitude (2)
40 A1 -- l_Hmag [>] indicates lower limit H-band magnitude
(records 647 to 668 only) (3)
41- 46 F6.3 mag Hmag TNG/NICS H-band (1.63um) magnitude
48- 52 F5.3 mag e_Hmag ? Uncertainty in H-band magnitude (4)
54 A1 -- l_H-K [><] indicate upper or lower limits H-K colour
index (records 647 to 812 only) (5)
55- 60 F6.3 mag H-K H-K colour index
62- 66 F5.3 mag e_H-K ? Uncertainty in H-K colour index (6)
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Note (1): Stars that were not detected in the K-band were assigned
K=18.48mag, the detection limit. This is therefore a lower limit to
the real K-mag and ">" was added in this case.
Note (2): For stars not detected in K-band, no uncertainty can be given and
in this case the entry is left blank
Note (3): Stars that were not detected in the H-band were assigned
H=19.52mag, the detection limit. This is therefore a lower limit to
the real H-mag and ">" was added in this case.
Note (4): For stars not detected in H-band, no uncertainty can be given and
in this case the entry is left blank
Note (5): For stars detected only in K- or H-band, the H-K colour is a
lower or upper limit, respectively. In this case, ">" or "<" was added.
Note (6): For stars with an upper or lower limit for H-K, no uncertainty
can be given and in this case the entry is left blank
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Acknowledgements:
Jan Brand, brand(at)ira.inaf.it
(End) Patricia Vannier [CDS] 21-Dec-2010