J/MNRAS/420/2884 NGC 1960 IRAC and MIPS photometry (Smith+, 2012)
Dust discs around intermediate-mass and Sun-like stars in the 16 Myr old
NGC 1960 open cluster.
Smith R., Jeffries R.D.
<Mon. Not. R. Astron. Soc., 420, 2884-2898 (2012)>
=2012MNRAS.420.2884S 2012MNRAS.420.2884S
ADC_Keywords: Clusters, open ; Photometry, millimetric/submm ; Stars, late-type
Keywords: circumstellar matter -
open clusters and associations: individual: NGC 1960 - infrared: stars
Abstract:
We present an analysis of Spitzer IRAC (3.6-8um) and MIPS (24um)
imaging of members of the 16+10-5 Myr old open cluster NGC 1960
(M36). Models of terrestrial planet formation indicate that rocky
planets are likely to achieve their final masses at around 10-30Myr,
and thus this cluster is at an interesting epoch for planet formation.
We find 21 B-F5 type stars and 14 F6-K9 type stars which have 24um
excess emission, and thus determine that >30 per cent of B-F5 type
stars and >23 per cent of F6-K9 type stars in this cluster have 24um
excess emission. These excess frequencies are similar to those
observed in other clusters of similar age. Three early-type stars have
excesses at near-infrared wavelengths. Analysis of their spectral
energy distributions confirms that these are true debris discs and not
remnant primordial or transitional discs. None of the 61 Sun-like
stars has confirmed near-infrared excess, and we can place a limit on
the frequency of 8um excess emission around Sun-like stars of <7 per
cent. All of the detected excesses are consistent with emission from
debris discs and are not primordial.
Description:
Data were sourced from the Spitzer Heritage Archive. Data were taken
with the IRAC and MIPS instruments under Spitzer Programme P50265.
IRAC data were obtained on 2008 October 23 in high dynamic range mode
using a 6x8 mapping array. MIPS data were obtained on 2008 November 1.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 46 63 Target sources in NGC 1960 from Sanner et al.
(2000, Cat. J/A+A/357/471)
table2.dat 47 69 The lower mass target sources in NGC 1960
table3.dat 92 63 Spitzer IRAC and MIPS 24um photometry for on
bright members of NGC 1960
table4.dat 98 67 Spitzer IRAC and MIPS 24um photometry for
low-mass members of NGC 1960
--------------------------------------------------------------------------------
See also:
J/A+A/357/471 : BV and proper motions in NGC 1960 + NGC 2194 (Sanner+, 2000)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- SAB Number from Sanner et al. 2000 (J/A+A/357/471)
<Cl* NGC 1960 SAB NNNN> in Simbad
4- 11 F8.5 deg RAdeg Right ascension in decimal degrees (J2000)
13- 20 F8.5 deg DEdeg Declination in decimal degrees (J2000)
21- 26 F6.3 mag V0mag Dereddened V magnitude (G1)
28- 33 F6.3 mag (B-V)0 Dereddened B-V colour index (G1)
35- 40 F6.3 mag (V-Ks)0 Dereddened V-Ks colour index (G1)
42- 46 I5 K Teff Effective temperature
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- ID Source designation, N_NNNN
8- 15 F8.5 deg RAdeg Right ascension in decimal degrees (J2000)
17- 24 F8.5 deg DEdeg Declination in decimal degrees (J2000)
25- 30 F6.3 mag V0mag Dereddened V magnitude (G1)
32- 36 F5.3 mag (B-V)0 Dereddened B-V colour index (G1)
38- 42 F5.3 mag (V-Ks)0 Dereddened V-Ks colour index (G1)
44- 47 I4 K Teff Effective temperature
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- SAB Number from Sanner et al. 2000 (J/A+A/357/471)
<Cl* NGC 1960 SAB NNNN> in Simbad
4- 9 F6.3 mag [3.6] Spitzer/IRAC 3.6um magnitude
11- 15 F5.3 mag e_[3.6] rms uncertainty on [3.6] (G2)
17- 22 F6.3 mag [4.5] Spitzer/IRAC 4.5um magnitude
24- 28 F5.3 mag e_[4.5] rms uncertainty on [4.5] (G2)
30- 35 F6.3 mag [5.8] Spitzer/IRAC 5.8um magnitude
37- 41 F5.3 mag e_[5.8] rms uncertainty on [5.8] (G2)
43- 48 F6.3 mag [8.0] Spitzer/IRAC 8.0um magnitude
50- 54 F5.3 mag e_[8.0] rms uncertainty on [8.0] (G2)
56 A1 --- l_[24] Limit flag on [24]
57- 62 F6.3 mag [24] Spitzer/MIPS 24um magnitude
64- 68 F5.3 mag e_[24] ? Spitzer/IRAC 24um magnitude
70 A1 --- l_Ks-[24] Limit flag on Ks-[24]
71- 76 F6.3 mag Ks-[24] Ks-[24] colour index
78 A1 --- l_F24/Fph Limit flag on F24/Fph
79- 84 F6.3 --- F24/Fph Ratio of 24µm to photospheric flux from
Plavchan et al. (2009ApJ...698.1068P 2009ApJ...698.1068P) relation
86- 92 A7 --- Com Comments (G3)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- ID Source designation, N_NNNN
8- 13 F6.3 mag [3.6] ?=- Spitzer/IRAC 3.6um magnitude
15- 19 F5.3 mag e_[3.6] ?=- rms uncertainty on [3.6] (G2)
21- 26 F6.3 mag [4.5] Spitzer/IRAC 4.5um magnitude
28- 32 F5.3 mag e_[4.5] rms uncertainty on [4.5] (G2)
34 A1 --- l_[5.8] Limit flag on [5.8]
35- 40 F6.3 mag [5.8] ?=- Spitzer/IRAC 5.8um magnitude
42- 46 F5.3 mag e_[5.8] ?=- rms uncertainty on [5.8] (G2)
48 A1 --- l_[8.0] Limit flag on [8.0]
49- 54 F6.3 mag [8.0] Spitzer/IRAC 8.0um magnitude
56- 60 F5.3 mag e_[8.0] ? rms uncertainty on [8.0] (G2)
62 A1 --- l_[24] Limit flag on [24]
63- 68 F6.3 mag [24] Spitzer/MIPS 24um magnitude
70- 74 F5.3 mag e_[24] ? Spitzer/IRAC 24um magnitude
76 A1 --- l_Ks-[24] Limit flag on Ks-[24]
77- 81 F5.3 mag Ks-[24] Ks-[24] colour index
83 A1 --- l_F24/Fph Limit flag on F24/Fph
84- 90 F7.3 --- F24/Fph Ratio of 24µm to photospheric flux from
Plavchan et al. (2009ApJ...698.1068P 2009ApJ...698.1068P) relation
92- 98 A7 --- Com Comments (G3)
--------------------------------------------------------------------------------
Global notes:
Note (G1): Magnitudes and colours corrected for reddening (using Av=0.775,
E(B-V)=0.25; Sanner et al. 2000, Cat. J/A+A/357/471, and E(V-Ks)=0.686
(and E(V-I)=0.400 for table2 only) using the relations from
Rieke & Lebofsky 1985ApJ...288..618R 1985ApJ...288..618R).
Note (G2): The error on the photospheric relation includes differences from
different photospheric predictions, variation in the colours observed for
sources without excess and statistical error on the 24um photometry added in
quadrature as described in the text.
Note (G3): Comments as follows:
Contam. = stars which had contaminating flux of more than 13% subtracted from
the aperture photometry. None of these targets have been
identified as a having confirm 24um excess.
XS = sources with Ks-[24] more than 3σ higher than the
photospheric relation from Plavchan et al. (2009ApJ...698.1068P 2009ApJ...698.1068P)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Oct-2012