J/MNRAS/499/993 Small Magellanic Cloud's background galaxies (Bell+, 2020)
The intrinsic reddening of the Magellanic Clouds as traced by background
galaxies - II. The Small Magellanic Cloud.
Bell C.P.M., Cioni M.-R.L., Wright A.H., Rubele S., Nidever D.L.,
Tatton B.L., van Loon J.T., Zaritsky D., Choi Y., Choudhury S.,
Clementini G., de Grijs R., Ivanov V.D., Majewski S.R., Marconi M.,
Martinez-Delgado D., Massana P., Munoz R.R., Niederhofer F., Noel N.E.D.,
Oliveira J.M., Olsen K., Pennock C.M., Ripepi V., Subramanian S.,
Vivas A.K.
<Mon. Not. R. Astron. Soc., 499, 993-1004 (2020)>
=2020MNRAS.499..993B 2020MNRAS.499..993B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Magellanic Clouds ; Redshifts ;
Reddening ; Optical ; Infrared
Keywords: surveys - dust, extinction - galaxies: ISM - Magellanic Clouds -
galaxies: photometry
Abstract:
We present a map of the total intrinsic reddening across ∼34deg2 of
the Small Magellanic Cloud (SMC) derived using optical (ugriz) and
near-infrared (IR; YJKs) spectral energy distributions (SEDs) of
background galaxies. The reddening map is created using a subsample of
29274 galaxies with low levels of intrinsic reddening based on the
LEPHARE χ2 minimization SED-fitting routine. We find
statistically significant enhanced levels of reddening associated with
the main body of the SMC compared with regions in the outskirts
[ΔE(B-V)∼0.3mag]. A comparison with literature reddening maps of
the SMC shows that, after correcting for differences in the volume of
the SMC sampled, there is good agreement between our results and maps
created using young stars. In contrast, we find significant
discrepancies between our results and maps created using old stars or
based on longer wavelength far-IR dust emission that could stem from
biased samples in the former and uncertainties in the far-IR
emissivity and the optical properties of the dust grains in the
latter. This study represents one of the first large-scale
categorizations of extragalactic sources behind the SMC and as such we
provide the LEPHARE outputs for our full sample of ∼500000 sources.
Description:
Our data set consists of optical ugriz and near-infrared (IR) YJKs
photometry taken as part of the SMASH and VMC surveys, respectively,
that cover the wavelength range 0.3-2.5µm. Paper I (Bell et al.
2019MNRAS.489.3200B 2019MNRAS.489.3200B) describes in detail the processes involved in
selecting likely background galaxies on which to perform photometry.
To briefly summarize, we use the VMC point-spread function (PSF)
photometric catalogues (Rubele et al. 2015MNRAS.449..639R 2015MNRAS.449..639R, Cat.
J/MNRAS/449/639, 2018MNRAS.478.5017R 2018MNRAS.478.5017R) and retain those sources that
satisfy the following colour-magnitude and morphological selections:
J-Ks>1.0mag, Ks>15mag, an associated stellar probability of less
than 0.33 and a Ks-band sharpness index of greater than 0.5.
Fluxes for each of our targets are measured using the Lambda Adaptive
Multi-Band Deblending Algorithm in R (LAMBDAR, v0.20.5; Wright et al.
2016MNRAS.460..765W 2016MNRAS.460..765W). Since Paper I, we have optimized the parameters
used for per-exposure PSF estimation within LAMBDAR, allowing for more
accurate PSF estimation per observation.
To ensure reliable fits to the SEDs, we only retain sources for which
we measure positive fluxes in at least four of the eight available
bands. Finally, we account for foreground Milky Way (MW) reddening by
de-reddening the individual fluxes by an amount equivalent to
E(B-V)=0.034mag. The resulting catalogue contains a total of 497577
sources (hereafter referred to as the full SMC sample) distributed
across ∼34deg2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 137 497577 A sample of the lephare output for the 497577
sources in the full SMC sample
table3.dat 53 46 Comparison between the spectroscopically
determined and calculated photometric redshifts
for QSOs behind the SMC
table4.dat 33 343 Median reddening values, standard deviations and
the number of galaxies in each of the 343 bins
covering the combined SMASH-VMC footprint of
the SMC
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- ID [1/497577]
8- 15 F8.5 deg RAdeg Right ascension (J2000)
17- 25 F9.5 deg DEdeg Declination (J2000)
27- 32 F6.4 --- zBEST Best-fitting photometric redshift
34- 41 F8.4 --- e_zBEST ?=-99 Lower error on zBEST (1σ limit)
43- 50 E8.4 --- E_zBEST ?=-99 Upper error on zBEST (1σ limit)
52- 59 F8.4 --- zML ?=-99 Maximum likelihood photometric redshift
61- 68 F8.4 --- e_zML ?=-99 Lower error on zML (1σ limit)
70- 77 F8.4 --- E_zML ?=-99 Upper error on zML (1σ limit)
79- 80 I2 --- TempG/Q Best-fitting galaxy/QSO template (1)
82- 97 E16.6 --- chi2G/Q Chi-squared for the best-fitting galaxy/QSO
template
99- 102 F4.2 mag E(B-V) Best-fitting reddening E (B-V)
104- 110 F7.4 mag mu Best-fitting distance modulus
112 I1 --- Nbands Number of photometric bands in the SED
114- 116 I3 --- Context Combination of photometric bands in the SED (2)
118- 120 I3 --- TempS Best-fitting stellar template
122- 137 E16.6 --- chi2S Chi-squared for the best-fitting stellar
template
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Note (1): Best-fitting galaxy/QSO templates are as follows: (1) Seyfert 1.8,
(2) Seyfert 2, (3) QSO1, (4) BQSO1, (5) TQSO1, (6) QSO2,
(7) Torus (QSO2), (8) Mrk 231, (9) IRAS 19254-7245, (10) NGC 6240,
(11-31) E, (32-47) Sbc, (48-58) Scd, (59-68) Irr, (69-72) Starburst
Note (2): Context is a numerical representation in lephare specifying the
combination of bandpasses present in the input catalogue and is
defined as Σi=1i=N2i-1, where i is the bandpass number
(in our case u=1, g=2, r=3, i=4, z=5, Y=6, J=7, and Ks=8), and N is
the total number of bandpasses.
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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- 23 A23 --- Name QSO name
25- 29 F5.3 --- zspec Spectroscopic redshift
31- 35 F5.3 --- zphot Calculated photometric redshift
37 A1 --- f_zphot [a] Flag on zphot (1)
39- 44 F6.3 --- e_zphot [] Lower error on zphot
46- 51 F6.3 --- E_zphot [] Upper error on zphot
53 I1 --- r_zspec Reference for zspec (2)
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Note (1): Flag as follows:
a = Associated 1σ limits on zphot are unphysical.
Note that despite having increased the uncertainties on the individual
LAMBDAR fluxes by a factor of 1.5 as well as including an additional
systematic uncertainty of 0.1mag in each of our eight bands, we find
that for ∼16 per cent of the sources classified as galaxies/QSOs in the
full SMC sample the associated 1σ limits on zBEST are unphysical
i.e. zBEST-1σ>zBEST or zBEST+1σ<zBEST.
Note (2): Reference as follows:
1 = Maitra et al. (2019A&A...622A..29M 2019A&A...622A..29M, Cat. J/A+A/622/A29)
2 = Kozlowski et al. (2013ApJ...775...92K 2013ApJ...775...92K, Cat. J/ApJ/775/92)
3 = Kozlowski, Kochanek & Udalski (2011ApJS..194...22K 2011ApJS..194...22K, Cat. J/ApJS/194/22)
4 = Public ESO Spectroscopic Survey of Transient Objects
(PESSTO; Smartt et al. 2015A&A...579A..40S 2015A&A...579A..40S, Cat. J/A+A/579/A40)
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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- 8 F8.5 deg RAdeg [] Right ascension (J2000)
10- 17 F8.5 deg DEdeg Declination (J2000)
19- 23 F5.3 mag E(B-V) Reddening
25- 29 F5.3 mag e_E(B-V) Error on E (B-V)
31- 33 I3 --- Ngal Number of galaxies
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History:
From electronic version of the journal
References:
Bell et al., Paper I 2019MNRAS.489.3200B 2019MNRAS.489.3200B
Bell et al., Paper III 2022MNRAS.516..824B 2022MNRAS.516..824B
(End) Ana Fiallos [CDS] 16-Aug-2023