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J/ApJS/230/9      Improved multi-band photometry from SERVS      (Nyland+, 2017)

An application of multi-band forced photometry to one square degree of SERVS: accurate photometric redshifts and implications for future science. Nyland K., Lacy M., Sajina A., Pforr J., Farrah D., Wilson G., Surace J., Haussler B., Vaccari M., Jarvis M. <Astrophys. J. Suppl. Ser., 230, 9-9 (2017)> =2017ApJS..230....9N (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, infrared ; Photometry, ugriz ; Surveys Keywords: catalogs; Galaxies: evolution; methods: data analysis; surveys; techniques: image processing Abstract: We apply The Tractor image modeling code to improve upon existing multi-band photometry for the Spitzer Extragalactic Representative Volume Survey (SERVS). SERVS consists of post-cryogenic Spitzer observations at 3.6 and 4.5µm over five well-studied deep fields spanning 18deg2. In concert with data from ground-based near-infrared (NIR) and optical surveys, SERVS aims to provide a census of the properties of massive galaxies out to z∼5. To accomplish this, we are using The Tractor to perform "forced photometry." This technique employs prior measurements of source positions and surface brightness profiles from a high-resolution fiducial band from the VISTA Deep Extragalactic Observations survey to model and fit the fluxes at lower-resolution bands. We discuss our implementation of The Tractor over a square-degree test region within the XMM Large Scale Structure field with deep imaging in 12 NIR/optical bands. Our new multi-band source catalogs offer a number of advantages over traditional position-matched catalogs, including (G1) consistent source cross-identification between bands, (2) de-blending of sources that are clearly resolved in the fiducial band but blended in the lower resolution SERVS data, (3) a higher source detection fraction in each band, (4) a larger number of candidate galaxies in the redshift range 5<z<6, and (5) a statistically significant improvement in the photometric redshift accuracy as evidenced by the significant decrease in the fraction of outliers compared to spectroscopic redshifts. Thus, forced photometry using The Tractor offers a means of improving the accuracy of multi-band extragalactic surveys designed for galaxy evolution studies. We will extend our application of this technique to the full SERVS footprint in the future. Description: The Spitzer Extragalactic Representative Volume Survey (SERVS) sky footprint includes five well-studied astronomical deep fields with abundant multi-wavelength data spanning an area of ∼18deg2 and a co-moving volume of ∼0.8Gpc3. The five deep fields included in SERVS are the XMM-LSS field, Lockman Hole (LH), ELAIS-N1 (EN1), ELAIS-S1 (ES1), and Chandra Deep Field South (CDFS). SERVS provides NIR, post-cryogenic imaging in the 3.6 and 4.5um Spitzer/IRAC bands to a depth of ∼2uJy. IRAC dual-band source catalogs generated using traditional catalog extraction methods are described in Mauduit+ (2012PASP..124..714M). The Spitzer IRAC data are complemented by ground-based NIR observations from the VISTA Deep Extragalactic Observations (VIDEO; Jarvis+ 2013MNRAS.428.1281J) survey in the south in the Z, Y, J, H, and Ks bands and UKIRT Infrared Deep Sky Survey (UKIDSS; Lawrence+ 2007, see II/319) in the north in the J and K bands. SERVS also provides substantial overlap with infrared data from SWIRE (Lonsdale+ 2003PASP..115..897L) and the Herschel Multitiered Extragalactic Survey (HerMES; Oliver+ 2012, VIII/95). As shown in Figure 1, one square degree of the XMM-LSS field overlaps with ground-based optical data from the Canada-France-Hawaii Telescope Legacy Survey Deep field 1 (CFHTLS-D1). The CFHTLS-D1 region is centered at RAJ2000=02:25:59, DEJ2000=-04:29:40 and includes imaging through the filter set u', g', r', i', and z'. Thus, in combination with the NIR data from SERVS and VIDEO that overlap with the CFHTLS-D1 region, multi-band imaging over a total of 12 bands is available. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file t4_irac.dat 956 8441 *IRAC-selected output Tractor catalogs t4_video.dat 988 117281 *VISTA Deep Extragalactic Observations (VIDEO)-selected output Tractor catalogs
Note on t4_*: The Tractor (Lang+ 2016AJ....151...36L; http://www.ascl.net/1604.008) uses prior source positions, fluxes, and shape information from a high-resolution, ground-based NIR fiducial band to model and fit the flux in the remaining NIR and optical bands. See section 3 for further explanations.
See also: III/334 : VISTA Deep Extragalactic Observations (VIDEO) (Jarvis+, 2013) II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012) VIII/95 : Herschel Multi-tiered Extragalactic Survey (Oliver+, 2012) II/317 : The CFHTLS Survey (T0007 release) (Hudelot+ 2012) J/ApJ/592/728 : Lyman break galaxies at redshift z∼3 (Steidel+, 2003) J/ApJ/690/1236 : COSMOS photometric redshift catalog (Ilbert+, 2009) J/ApJS/219/39 : QSOs selection from SDSS and WISE (Richards+, 2015) J/A+A/579/A115 : SUDARE-VOICE variability-selection of AGN (Falocco+, 2015) J/A+A/590/A31 : ASTRODEEP Frontier Fields Catalogues (Merlin+, 2016) J/ApJS/225/1 : SpIES: the Spitzer IRAC Equatorial Survey (Timlin+, 2016) http://irsa.ipac.caltech.edu/data/SPITZER/SERVS/ : SERVS data on IRSA Byte-by-byte Description of file: t4_irac.dat
Bytes Format Units Label Explanations
1- 9 F9.6 deg RAdeg Right Ascension, decimal degrees (J2000) 11- 20 F10.7 deg DEdeg Declination, decimal degrees (J2000) 22- 39 E18.11 uJy FKs [-0.6/4660]? VIDEO VISTA Ks-band flux (G1) 41- 58 E18.11 uJy FH [-0.4/5003]? VIDEO VISTA H-band flux (G1) 60- 77 E18.11 uJy FJ [-0.4/3790]? VIDEO VISTA J-band flux (G1) 79- 96 E18.11 uJy FY [-0.4/4660]? VIDEO VISTA Y-band (1.018um) flux (G1) 98-115 E18.11 uJy FZ [-0.4/3952]? VIDEO VISTA Z-band (0.8762um) flux (G1) 117-134 E18.11 uJy Fi' [-4541/880]? CFHTLS-D1 CFHT i'-band flux (G1) 136-153 E18.11 uJy Fr' [-1314/946]? CFHTLS-D1 CFHT r'-band flux (G1) 155-172 E18.11 uJy Fg' [-32524/658]? CFHTLS-D1 CFHT g'-band flux (G1) 174-191 E18.11 uJy Fz'C [-2230/88906]? CFHTLS-D1 CFHT z'-band flux (G1) 193-210 E18.11 uJy Fu' [-614934/17565]? CFHTLS-D1 CFHT u'-band flux (G1) 212-229 E18.11 uJy F3.6 [-108/4470]? SERVS Spitzer/IRAC 3.6um flux (G1) 231-248 E18.11 uJy F4.5 [-19/2629]? SERVS Spitzer/IRAC 4.5um flux (G1) 250-263 F14.10 uJy e_FKs [0.1/420]? Uncertainty in FKs 265-278 F14.10 uJy e_FH [0.07/451]? Uncertainty in FH 280-293 F14.10 uJy e_FJ [0.04/342]? Uncertainty in FJ 295-308 F14.10 uJy e_FY [0.03/420]? Uncertainty in FY 310-323 F14.10 uJy e_FZ [0.02/356]? Uncertainty in FZ 325-338 F14.10 uJy e_Fi' [0.003/137]? Uncertainty in Fi' 340-352 F13.10 uJy e_Fr' [0.002/40]? Uncertainty in Fr' 354-367 F14.10 uJy e_Fg' [0.001/976]? Uncertainty in Fg' 369-383 F15.10 uJy e_Fz'C [0.008/2668]? Uncertainty in Fz'C 385-400 F16.10 uJy e_Fu' [0.002/18449]? Uncertainty in Fu' 402-413 F12.10 uJy e_F3.6 [0.3/0.9]? Uncertainty in F3.6 415-426 F12.10 uJy e_F4.5 [0.5/0.8]? Uncertainty in F4.5 428-437 F10.7 mag Ksmag [14.7/36.8]? VIDEO Ks-band AB magnitude 439-448 F10.7 mag Hmag [14.6/32.6]? VIDEO H-band AB magnitude 450-459 F10.7 mag Jmag [14.9/35.4]? VIDEO J-band AB magnitude 461-470 F10.7 mag Ymag [14.7/32.3]? VIDEO Y-band AB magnitude 472-481 F10.7 mag Zmag [14.9/36.7]? VIDEO Z-band AB magnitude 483-492 F10.7 mag i'mag [16.5/35.1]? CFHTLS-D1 i'-band AB magnitude 494-503 F10.7 mag r'mag [16.4/34.5]? CFHTLS-D1 r'-band AB magnitude 505-514 F10.7 mag g'mag [16.8/35.5]? CFHTLS-D1 g'-band AB magnitude 516-525 F10.7 mag z'Cmag [11.5/33.4]? CFHTLS-D1 z'-band AB magnitude 527-536 F10.7 mag u'mag [13.2/35.5]? CFHTLS-D1 u'-band AB magnitude 538-547 F10.7 mag 3.6mag [14.7/30.3]? SERVS [3.6] AB magnitude 549-558 F10.7 mag 4.5mag [15.3/32.8]? SERVS [4.5] AB magnitude 560-574 F15.9 mag e_Ksmag [0.09/15617]? Uncertainty in Ksmag 576-588 F13.9 mag e_Hmag [0.09/223]? Uncertainty in Hmag 590-603 F14.9 mag e_Jmag [0.09/1905]? Uncertainty in Jmag 605-617 F13.9 mag e_Ymag [0.09/105]? Uncertainty in Ymag 619-632 F14.9 mag e_Zmag [0.09/3107]? Uncertainty in Zmag 634-646 F13.9 mag e_i'mag [0.03/129]? Uncertainty in i'mag 648-659 F12.9 mag e_r'mag [0.03/49]? Uncertainty in r'mag 661-672 F12.9 mag e_g'mag [0.03/88]? Uncertainty in g'mag 674-685 F12.9 mag e_z'Cmag [0.03/56]? Uncertainty in z'Cmag 687-699 F13.9 mag e_u'mag [0.03/127]? Uncertainty in u'mag 701-713 F13.9 mag e_3.6mag [0.0001/134]? Uncertainty in 3.6mag 715-728 F14.9 mag e_4.5mag [0.0003/1836]? Uncertainty in 4.5mag 730-746 E17.11 --- rChiKs ? Tractor reduced chi squared profile fit, Ks (redchi-Ks) 748-764 E17.11 --- rChiH ? Tractor reduced chi squared profile fit, H (redchi-H) 766-782 E17.11 --- rChiJ ? Tractor reduced chi squared profile fit, J (redchi-J) 784-800 E17.11 --- rChiZ ? Tractor reduced chi squared profile fit, Z (redchi-Z) 802-818 E17.11 --- rChiY ? Tractor reduced chi squared profile fit, Y (redchi-Y) 820-836 E17.11 --- rChii' ? Tractor reduced chi squared profile fit, i' (redchi-i') 838-854 E17.11 --- rChir' ? Tractor reduced chi squared profile fit, r' (redchi-i') 856-872 E17.11 --- rChig' ? Tractor reduced chi squared profile fit, g' (redchi-g') 874-890 E17.11 --- rChiz'C ? Tractor reduced chi squared profile fit, z'C (redchi-z'C) 892-908 E17.11 --- rChiu' ? Tractor reduced chi squared profile fit, u' (redchi-u') 910-926 E17.11 --- rChi3.6 [0.4/594125]? Tractor reduced chi squared profile fit, 3.6um (redchi-3.6) 928-944 E17.11 --- rChi4.5 [0.4/141297]? Tractor reduced chi squared profile fit, 4.5um (redchi-4.5) 946-950 A5 --- Band VIDEO band ([3.6] or [4.5]) used to define source model (Fiducialband) 952-956 A5 --- Mod [PtSrc] Source surface brightness profile model (all "PtSrc"=point source model) (SourceModel)
Byte-by-byte Description of file: t4_video.dat
Bytes Format Units Label Explanations
1- 9 F9.6 deg RAdeg Right Ascension, decimal degrees (J2000) 11- 20 F10.7 deg DEdeg Declination, decimal degrees (J2000) 22- 39 E18.11 uJy FKs [-56/187650]? VIDEO VISTA Ks-band flux (G1) 41- 58 E18.11 uJy FH [-44/203387]? VIDEO VISTA H-band flux (G1) 60- 77 E18.11 uJy FJ [-29/152366]? VIDEO VISTA J-band flux (G1) 79- 96 E18.11 uJy FY [-23/279636]? VIDEO VISTA Y-band flux (G1) 98-115 E18.11 uJy FZ [-17/181329]? VIDEO VISTA Z-band flux (G1) 117-134 E18.11 uJy Fi' [-16031/31876]? CFHTLS-D1 CFHT i'-band flux (G1) 136-153 E18.11 uJy Fr' [-18950/39642]? CFHTLS-D1 CFHT r'-band flux (G1) 155-172 E18.11 uJy Fg' [-18804/266199]? CFHTLS-D1 CFHT g'-band flux (G1) 174-191 E18.11 uJy Fz'C [-130457/]? CFHTLS-D1 CFHT z'-band flux (G1) 193-210 E18.11 uJy Fu' [-14150/34689]? CFHTLS-D1 CFHT u'-band flux (G1) 212-229 E18.11 uJy F3.6 [-50/58703]? SERVS Spitzer/IRAC 3.6um flux (G1) 231-248 E18.11 uJy F4.5 [-152/71428]? SERVS Spitzer/IRAC 4.5um flux (G1) 250-265 F16.10 uJy e_FKs [0.1/16889]? Uncertainty in FKs 267-282 F16.10 uJy e_FH [0.1/18305]? Uncertainty in FH 284-299 F16.10 uJy e_FJ [0.08/13713]? Uncertainty in FJ 301-316 F16.10 uJy e_FY [0.06/25168]? Uncertainty in FY 318-333 F16.10 uJy e_FZ [0.03/16320]? Uncertainty in FZ 335-348 F14.10 uJy e_Fi' [0.005/957]? Uncertainty in Fi' 350-364 F15.10 uJy e_Fr' [0.004/1190]? Uncertainty in Fr' 366-380 F15.10 uJy e_Fg' [0.003/7986]? Uncertainty in Fg' 382-397 F16.10 uJy e_Fz'C [0.01/32298]? Uncertainty in Fz'C 399-413 F15.10 uJy e_Fu' [0.005/1201]? Uncertainty in Fu' 415-426 F12.10 uJy e_F3.6 [0.3/2.7]? Uncertainty in F3.6 428-439 F12.10 uJy e_F4.5 [0.2/1.6]? Uncertainty in F4.5 441-450 F10.7 mag Ksmag [10.7/31.7]? VIDEO Ks-band AB magnitude 452-461 F10.7 mag Hmag [10.6/33.8]? VIDEO H-band AB magnitude 463-472 F10.7 mag Jmag [10.9/34.5]? VIDEO J-band AB magnitude 474-483 F10.7 mag Ymag [10.2/33]? VIDEO Y-band AB magnitude 485-494 F10.7 mag Zmag [10.7/35.4]? VIDEO Z-band AB magnitude 496-505 F10.7 mag i'mag [12.6/35.5]? CFHTLS-D1 i'-band AB magnitude 507-516 F10.7 mag r'mag [12.4/38]? CFHTLS-D1 r'-band AB magnitude 518-527 F10.7 mag g'mag [10.3/37.7]? CFHTLS-D1 g'-band AB magnitude 529-538 F10.7 mag z'Cmag [8.8/36.2]? CFHTLS-D1 z'-band AB magnitude 540-549 F10.7 mag u'mag [12.5/36.3]? CFHTLS-D1 u'-band AB magnitude 551-560 F10.7 mag 3.6mag [11.9/33.5]? SERVS [3.6] AB magnitude 562-571 F10.7 mag 4.5mag [11.7/34.6]? SERVS [4.5] AB magnitude 573-585 F13.9 mag e_Ksmag [0.09/352]? Uncertainty in Ksmag 587-600 F14.9 mag e_Hmag [0.09/1249]? Uncertainty in Hmag 602-615 F14.9 mag e_Jmag [0.09/2108]? Uncertainty in Jmag 617-629 F13.9 mag e_Ymag [0.09/406]? Uncertainty in Ymag 631-644 F14.9 mag e_Zmag [0.09/2106]? Uncertainty in Zmag 646-658 F13.9 mag e_i'mag [0.03/390]? Uncertainty in i'mag 660-673 F14.9 mag e_r'mag [0.03/3027]? Uncertainty in r'mag 675-688 F14.9 mag e_g'mag [0.03/1613]? Uncertainty in g'mag 690-703 F14.9 mag e_z'Cmag [0.03/1737]? Uncertainty in z'Cmag 705-718 F14.9 mag e_u'mag [0.06/1308]? Uncertainty in u'mag 720-733 F14.9 mag e_3.6mag [/2439]? Uncertainty in 3.6mag 735-748 F14.9 mag e_4.5mag [/5161]? Uncertainty in 4.5mag 750-766 E17.11 --- rChiKs ? Tractor reduced chi squared profile fit, Ks (redchi-Ks) 768-784 E17.11 --- rChiH ? Tractor reduced chi squared profile fit, H (redchi-H) 786-802 E17.11 --- rChiJ ? Tractor reduced chi squared profile fit, J (redchi-J) 804-820 E17.11 --- rChiZ ? Tractor reduced chi squared profile fit, Z (redchi-Z) 822-838 E17.11 --- rChiY ? Tractor reduced chi squared profile fit, Y (redchi-Y) 840-856 E17.11 --- rChii' ? Tractor reduced chi squared profile fit, i' (redchi-i') 858-874 E17.11 --- rChir' ? Tractor reduced chi squared profile fit, r' (redchi-r') 876-892 E17.11 --- rChig' ? Tractor reduced chi squared profile fit, g' (redchi-g') 894-910 E17.11 --- rChiz'C ? Tractor reduced chi squared profile fit, z'C (redchi-z'C) 912-928 E17.11 --- rChiu' ? Tractor reduced chi squared profile fit, u' (redchi-u') 930-946 E17.11 --- rChi3.6 ? Tractor reduced chi squared profile fit, 3.6um (redchi-3.6) 948-964 E17.11 --- rChi4.5 ? Tractor reduced chi squared profile fit, 4.5um (redchi-4.5) 966-967 A2 --- Band VIDEO band (JHKsYZ) used to define source model (Fiducialband) 969-973 A5 --- Mod Source surface brightness profile model (SourceModel) (1) 975 I1 --- f_Ks Source saturation flag in Ks (1=saturated) (Sat-flag) (2) 976 I1 --- f_H Source saturation flag in H-band (1=saturated) (Sat-flag) (2) 977 I1 --- f_J Source saturation flag in J-band (1=saturated) (Sat-flag) (2) 978 I1 --- f_Y Source saturation flag in Y-band (1=saturated) (Sat-flag) (2) 979 I1 --- f_Z Source saturation flag in Z-band (1=saturated) (Sat-flag) (2) 980 I1 --- f_i' Source saturation flag in i' (1=saturated) (Sat-flag) (2) 981 I1 --- f_r' Source saturation flag in r' (1=saturated) (Sat-flag) (2) 982 I1 --- f_g' Source saturation flag in g' (1=saturated) (Sat-flag) (2) 983 I1 --- f_z' Source saturation flag in z' (1=saturated) (Sat-flag) (2) 984 I1 --- f_u' Source saturation flag in u' (1=saturated) (Sat-flag) (2) 985 I1 --- f_3.6um Source saturation flag in 3.6um (1=saturated) (Sat-flag) (2) 986 I1 --- f_4.5um Source saturation flag in 4.5um (1=saturated) (Sat-flag) (2) 988 I1 --- Ffit Fit flag (Fit-flag) (3)
Note (1): Source surface brightness profile model as follows: Dev = deVaucouleurs profile (50774 occurrences); Exp = exponential profile (25748 occurrences); PtSrc = point source model (40759 occurrences). Note (2): Source saturation flags are a single binary string containing a 0 (not saturated) or a 1 (saturated) for each band. The Sat-Flag columns are only included for the VIDEO-selected catalog since saturation is not an issue in the IRAC-selected catalog of intrinsically fainter sources. Note (3): Fit-Flag = 1 are instances where the Tractor fit did not converge (often related to poor initial constraints from the source properties in the fiducial band, e.g., when no source is actually present). In the original tabulation the fluxes were +Inf; the magnitudes -Inf.
Global notes: Note (G1): Negative fluxes are retained in the catalog and correspond to objects with null magnitude measurements. Negative fluxes can be useful for SED fitting, and also to allow an estimate of the distribution of fluxes for a population of faint sources for use in stacking analyses.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Jul-2017
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