J/ApJ/730/78 Hubble and Spitzer photometry of NGC 602 (Carlson+, 2011)
A panchromatic view of NGC 602: time-resolved star formation with the Hubble and
Spitzer space telescopes.
Carlson L.R., Sewilo M., Meixner M., Romita K.A., Whitney B., Hora J.L.,
Cignoni M., Sabbi E., Nota A., Sirianni M., Smith L.J., Gordon K.,
Babler B., Bracker S., Gallagher J.S., Meade M., Misselt K., Pasquali A.,
Shiao B.
<Astrophys. J., 730, 78 (2011)>
=2011ApJ...730...78C 2011ApJ...730...78C
ADC_Keywords: YSOs ; Clusters, open ; Photometry, HST ; Photometry, infrared
Keywords: ISM: individual objects (NGC 602, N90) - Magellanic Clouds -
stars: formation - stars: pre-main sequence - stars: protostars
Abstract:
We present the photometric catalogs for the star-forming cluster
NGC 602 in the wing of the Small Magellanic Cloud covering a range of
wavelengths from optical (HST/ACS F555W, F814W, and SMARTS/ANDICAM V,
I) to infrared (Spitzer/IRAC 3.6, 4.5, 5.8, and 8um and MIPS 24um).
Combining this with Infrared Survey Facility near-infrared photometry
(J, H, Ks), we compare the young main sequence (MS) and pre-main
sequence (PMS) populations prominent in the optical with the current
young stellar object (YSO) populations revealed by the infrared. We
analyze the MS and PMS population with isochrones in color-magnitude
diagrams to derive ages and masses. The optical data reveal ∼565 PMS
candidates, low-mass Stage III YSOs. We characterize ∼40 YSOs by
fitting their spectral energy distributions to a grid of models
(Robitaille et al. 2007ApJS..169..328R 2007ApJS..169..328R) to derive luminosities,
masses, and evolutionary phase (Stages I-III). The higher resolution
HST images reveal that ∼70% of the YSO candidates are either multiples
or protoclusters. For YSOs and PMS sources found in common, we find a
consistency in the masses derived. We use the YSO mass function to
derive a present-day star formation rate of ∼0.2-1.0M☉/yr/kpc2,
similar to the rate derived from the optical star formation history
suggesting a constant star formation rate for this region.
Description:
Observations of NGC 602 (J2000=01:29:31-73:33:15) were taken from the
optical to the mid-IR (Figure 2). We use optical data primarily from
the HST/ACS Wide Field Channel (WFC) in F555W (V), F658N (Hα),
and F814W (I). We add ground-based observations from the SMARTS (Small
and Moderate Aperture Research Telescope System) ANDICAM instrument on
a 1.3m telescope in Johnson-Cousins V and I bands.
Five mid-IR images were taken through each of the four Spitzer/IRAC
bands (Program ID 125, PI: Fazio, AOR 12485120). We also use near-IR
photometry from the Magellanic Clouds Point Source Catalog of Kato et
al. (2007, Cat. II/288). This imaging survey was performed with the
simultaneous three-color Infrared Imager for Unbiased Surveys (SIRIUS)
aboard the Infrared Survey Facility (IRSF) 1.4m telescope at the
South African Astronomical Observatory's Southland.
Multiwavelength Imaging Photometer for Spitzer (MIPS) 24um data are
taken from the first epoch observations of SAGE-SMC (K. Gordon et al.
2011AJ....142..102G 2011AJ....142..102G). These observations were performed in 2007
October.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 98 4535 Optical photometry table
table3.dat 201 500 IRAC photometry table
table4.dat 202 81 Fluxes of all 77 fitter sources including those
fit in multiple ways
table5.dat 107 51 *Young stellar object parameters
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Note on table5.dat: For those sources with optical counterparts, we list the
number of visually identifiable optical sources. Where possible, we determine
masses of the optical sources; others either have no good optical photometry
or are so young or of such low mass (M≲0.5M☉) that their masses cannot
be determined from our evolutionary tracks (see Figure 3 (b)).
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See also:
II/288 : IRSF Magellanic Clouds Point Source Catalog (Kato+ 2007)
II/305 : SAGE LMC and SMC IRAC Source Catalog (IPAC 2009)
J/ApJ/681/290 : HST/ACS photometry in the SMC (Schmalzl+, 2008)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/4535] Source index number
6- 14 A9 --- --- [HSTNGC602]
16- 36 A21 --- Name Source designation (JHHMMSS.sss+DDMMSS.ss)
38- 45 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
47- 55 F9.5 deg DEdeg Declination in decimal degrees (J2000)
57- 62 F6.3 mag Vmag ?=0 HST/ACS F555W filter magnitude
64- 68 F5.3 mag e_Vmag ?=0 Uncertainty in Vmag
70- 75 F6.3 mag Imag [13.51/27.91] HST/ACS F814W filter magnitude
77- 81 F5.3 mag e_Imag Uncertainty in Imag
83- 84 I2 --- s [2/12] Source of photometry (1)
86- 89 I4 --- S08 Schmalzl et al. 2008, Cat. J/ApJ/681/290
identifier (<Cl* NGC 602 SGD NNNN> for Simbad)
91- 92 I2 --- H91 ?=0 Hutchings et al. 1991AJ....101..933H 1991AJ....101..933H
spectroscopic O/B star number
(<Cl* NGC 602 HTCP NN> in Simbad)
94- 96 I3 --- IRAC [1/598]?=0 Matching IRAC source identifier from
Table 3
98 I1 --- N [0/9] Total number of optical sources matching
the same IRAC source
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Note (1): Flags indicate the photometric data used:
2 = ACS;
6 = ground-based (SMARTS);
12 = ACS/SMARTS combination.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [7/703] Source index number
5- 34 A30 --- Name Source designation
(SSTNGC602/SSTISAGE1A JHHMMSS.ss+DDMMSS.s)
36 A1 --- f_Name [f] Flag for SAGE name (1)
38- 46 A9 --- OName Other identifier (G1)
48- 58 F11.8 deg RAdeg Right Ascension in decimal degrees (J2000)
60- 71 F12.8 deg DEdeg Declination in decimal degrees (J2000)
73- 78 F6.3 mag [3.6] ?=99.99 Spitzer/IRAC 3.6 micron band magnitude
80- 85 F6.3 mag e_[3.6] ?=99.99 Uncertainty in [3.6]
87- 92 F6.3 mag [4.5] ?=99.99 Spitzer/IRAC 4.5 micron band magnitude
94- 99 F6.3 mag e_[4.5] ?=99.99 Uncertainty in [4.5]
101-106 F6.3 mag [5.8] ?=99.99 Spitzer/IRAC 5.8 micron band magnitude
108-113 F6.3 mag e_[5.8] ?=99.99 Uncertainty in [5.8]
115-121 F7.3 mag [8.0] ?=99.99 Spitzer/IRAC 8.0 micron band magnitude
123-128 F6.3 mag e_[8.0] ?=99.99 Uncertainty in [8.0]
130-135 F6.3 mag [24] ?=99.99 Spitzer/MIPS 24 micron band magnitude
137-142 F6.3 mag e_[24] ?=99.99 Uncertainty in [24]
144 I1 --- N [0/2] Total number of optical sources matching
the same IRAC source
146-192 A47 --- Match ID(s)s of all optical sources matched from
Table 2
194-195 I2 --- H91 [1/12]?=0 Hutchings et al. 1991AJ....101..933H 1991AJ....101..933H
spectroscopic O/B star number
197-201 A5 --- G07 Gouliermis et al. 2007ApJ...665..306G 2007ApJ...665..306G YSO
candidate identifier(s) (<[GQH2007] NN> in
Simbad)
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Note (1): Source designation from SAGE-SMC (Surveying the Agents of Galaxy
Evolution in the SMC; K. Gordon et al. 2011AJ....142..102G 2011AJ....142..102G,
2011AJ....142..103B 2011AJ....142..103B); see Cat. II/305
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Source name, <[CSM2011] NNN> in Simbad
5 A1 --- n_ID [io] Notes for source 270 (1)
7- 36 A30 --- Name IRAC designation
(SSTNGC602/SSTISAGE1A JHHMMSS.ss+DDMMSS.s)
38- 45 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
47- 55 F9.5 deg DEdeg Declination in decimal degrees (J2000)
57- 62 F6.4 mJy F(V) ? HST/ACS F555W filter flux density (2)
64- 69 F6.4 mJy e_F(V) ? Uncertainty in S(V) (3)
71- 77 F7.4 mJy F(I) ? HST/ACS F814W filter flux density (2)
79- 84 F6.4 mJy e_F(I) ? Uncertainty in S(I) (3)
86- 92 F7.4 mJy F(J) ? IRSF J band flux density (4)
94- 99 F6.4 mJy e_F(J) ? Uncertainty in S(J) (3)
101-107 F7.4 mJy F(H) ? IRSF H band flux density (4)
109-114 F6.4 mJy e_F(H) ? Uncertainty in S(K) (3)
116-122 F7.4 mJy F(K) ? IRSF KS band flux density (4)
124-129 F6.4 mJy e_F(K) ? Uncertainty in S(K) (3)
131-137 F7.4 mJy F(3.6) Spitzer/IRAC 3.6 micron band flux density
139-144 F6.4 mJy e_F(3.6) Uncertainty in S(3.6) (3)
146-152 F7.4 mJy F(4.5) ? Spitzer/IRAC 4.5 micron band flux density
154-159 F6.4 mJy e_F(4.5) ? Uncertainty in S(4.5) (3)
161-166 F6.4 mJy F(5.8) ? Spitzer/IRAC 5.8 micron band flux density
168-173 F6.4 mJy e_F(5.8) ? Uncertainty in S(5.8) (3)
175-180 F6.4 mJy F(8.0) ? Spitzer/IRAC 8.0 micron band flux density
182-187 F6.4 mJy e_F(8.0) ? Uncertainty in S(8.0) (3)
189-195 F7.4 mJy F(24) ? Spitzer/MIPS 24 micron band flux density
197-202 F6.4 mJy e_F(24) ? Uncertainty in S(24) (3)
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Note (1): Optically, source 270 appears to be a protocluster emerging from a
pillar of dust (Figure 12). We fit source 270 in the three ways shown
in Figure 12: (A270) fitting all data points, (Y270o) fitting optical
plus NIR, and (Y270i) fitting IRAC plus MIPS 24um. See section 4.7.2
for further explanations.
Note (2): Calculated from aperture photometry magnitudes, which are adapted
from ACS/WFC F555W and F814W bands to V and I according to the
prescription of Sirianni et al. (2005PASP..117.1049S 2005PASP..117.1049S).
Note (3): Where 0.90 or 0.95 are reported in the error columns that data point
is set as an upper with 0.90 or 0.95 certainty.
Note (4): Adapted from IRSF to 2MASS as described in Kato et al. (2007,
Cat. II/288).
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name YSO designation (G1)
8- 12 A5 --- f_Name [fghk, ] Flag on Name (1)
14- 18 A5 --- G07 Identification number(s) from Gouliermis
et al. (2007ApJ...665..306G 2007ApJ...665..306G;
<[GQH2007] NN> in Simbad)
20 A1 --- l_Nopt Limit flag on Nopt
21- 22 I2 --- Nopt ? Approximate number of optical sources
within the 1.6" IRAC aperture radius
23 A1 --- f_Nopt [il] Flag on Nopt (1)
25- 28 F4.2 --- Chi2 χ2min (cpd) per data point
30- 33 I4 --- Nfits Number of fits with cpd between cpdmin
and cpdmin+0.5
35- 39 F5.2 Msun Mopt ? Sum of the optical masses
40 A1 --- f_Mopt [j] Flag on Mopt (1)
42- 46 F5.2 Msun <M*> ? Mean IR mass
48- 51 F4.2 Msun e_<M*> ? Standard deviation of <M*>
53- 58 F6.3 10+3Lsun <L*> ? Luminosity
60 A1 --- le<L*> Limit flag on e_<L*>
61- 65 F5.3 10+3Lsun e_<L*> ? Uncertainty on <L*>
67 A1 --- l_dM/dt Limit flag on dM/dt
68- 74 F7.3 10-4Msun/yr dM/dt ? Accretion rate
76 A1 --- ledM/dt Limit flag on e_dM/dt
77- 82 F6.3 10-4Msun/yr e_dM/dt ? Uncertainty on dM/dt
84 A1 --- l_<Mdisk> Limit flag on <Mdisk>
85- 91 F7.5 Msun <Mdisk> ? Disk mass
93 A1 --- le<Mdisk> Limit flag on e_<Mdisk>
94- 99 F6.4 Msun e_<Mdisk> ? Uncertainty on <Mdisk>
101-107 A7 --- Stage Evolutionary stage (U=unclassified
probable YSO)
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Note (1): Flag as follows:
f = These sources are likely YSOs based on CMD examination and physical
location, but they are not considered well fit.
g = These sources are fit with optical fluxes set as upper limits.
h = Fit using the error bar method of correcting for PAH emission.
k = These are in environments of illuminated dust, mostly along ridges or in
the tips of "pillars".
i = Corresponds to one or more PMS star.
j = These optical masses neglect one or more optical source.
l = Outside optical FOV.
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Global note:
Note (G1): ID number with prefixes: Y (YSO candidate), G (galaxy),
K (naked star), S (stellar in images but not fit), and U (unclassified);
NA= Not applicable (see "[CSM2011]" column of table 4). See section 2.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 17-Sep-2012