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The Spitzer Space Telescope Extra-Galactic First Look Survey: 24 micron data reduction, catalog, and source identification

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Dario Fadda, F. R. Marleau, L. J. Storrie-Lombardi, D. Makovoz, D. T. Frayer, P. N. Appleton, L. Armus, S. C. Chapman (1)
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P. I. Choi, F. Fang, I. Heinrichsen, G. Helou, M. Im (2), M. Lacy, D. L. Shupe, B. T. Soifer, G. K. Squires, J. Surace, H. I. Teplitz, G. Wilson, L. Yan, (Spitzer Science Center - Caltech expect (1) Dep. of Astronomy - Caltech, (2) Seoul National University.)

Astrophysics · Submitted 17 Mar 2006 · 31 references

Pith's verdict: A careful 24 micron survey catalog with real reduction innovations; the completeness simulations are self-referential in a way that runs conservative, so the central claims hold.

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arXiv IDastro-ph/0603488 (version 1)
Pith IDEUQGZRA6, Pith's permanent record of this paper and its review
Citation(2) Seoul National University.), B. T. Soifer, Dario Fadda, D. L. Shupe, D. Makovoz, D. T. Frayer, F. Fang, F. R. Marleau, G. Helou, G. K. Squires, G. Wilson, H. I. Teplitz, I. Heinrichsen, J. Surace, L. Armus, L. J. Storrie-Lombardi, L. Yan, M. Im (2), M. Lacy, P. I. Choi, P. N. Appleton, S. C. Chapman (1), (Spitzer Science Center - Caltech expect (1) Dep. of Astronomy - Caltech. "The Spitzer Space Telescope Extra-Galactic First Look Survey: 24 micron data reduction, catalog, and source identification." arXiv:astro-ph/0603488 (2006). https://pith.science/paper/EUQGZRA6
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The paper

The paper claims

The paper delivers a public catalog of 16,905 Spitzer 24 micron point sources, 50% complete at 0.3 mJy (main) and 0.15 mJy (verification), with optical counterparts for over 80% of sources.

The reading

This paper argues that a deliberately self-calibrated reduction of Spitzer MIPS 24 micron images from the First Look Survey yields a reliable public catalog of 16,905 point sources detected at signal-to-noise above 5, together with 123 resolved extended sources. The paper's key quantitative claims are that the main survey is 50% complete at 0.3 mJy, the deeper verification survey at 0.15 mJy, that astrometric errors range from 0.35 to 1 arcsecond and photometric errors from 5% to 15% depending on brightness, and that more than 80% of sources have reliable optical counterparts down to R=25.5. If correct, this gives the community a well-calibrated mid-infrared sample over roughly five square degrees of a new cosmological field, deep enough to detect luminous infrared galaxies up to redshift 2.5. The paper also shows that after subtracting point sources and masking extended ones, the residual image reveals Galactic cirrus clouds matching neutral hydrogen structures.

What carries the argument

The argument is carried by a self-calibrated reduction and extraction pipeline whose central object is the empirical point response function (PRF), built by stacking 27 bright isolated sources and used for both detection and PSF-fitting photometry. Around this core, the pipeline applies corrections for four-amplifier dark residuals and jail-bar latencies, scan-mirror illumination and zodiacal-light subtraction, a long-term transient model fitted to the median behavior of the scan legs, and relative astrometric offsets derived from optical counterparts. Source extraction is performed on a ringless image (bright sources with Airy rings removed) to suppress false detections, then refit on the original mosaic. Completeness, reliability, and error estimates come from simulations that reinsert extracted sources into the residual image and re-detect them using a 5-arcsecond and 30% flux matching criterion; the residual image itself is produced by subtracting 3-sigma point sources and interpolating over the regions occupied by extended sources.

Extended reading notes

Core claim

The paper reports that the First Look Survey 24 micron data, after correcting for four-amplifier dark-current patterns, jail-bar latencies, scan-mirror illumination variations, zodiacal light, and a long-term detector transient, can be mosaicked into an image from which source extraction is both deep and reliable. The resulting catalog contains 16,905 point sources with signal-to-noise ratio greater than 5; reinsertion simulations imply 50% completeness at 0.3 mJy in the main field and 0.15 mJy in the verification field, with reliability above 85% at the catalog flux limits. The quoted astrometric error follows $\sigma^2 = \sigma_{\rm ext}^2 + \sigma_{\rm point}^2$ with $\sigma_{\rm point} = 0.3$ arcsec and $\log(\sigma_{\rm ext}) = 0.74 - 1.06\log(\mathrm{SNR})$, while photometric errors grow from about 5% at SNR $\sim 20$ to about 15% at SNR $\sim 5$. The photometry uses an empirical point response function built from 27 bright isolated sources, an aperture correction checked on a bright star, and an absolute calibration verified on 224 field stars to within 0.5% of the official value. Cross-matching gives reliable optical counterparts for over 80% of the sources and 20 cm counterparts for about 16%, and the residual image, produced by subtracting 3-$\sigma$ point sources and interpolating over extended sources, reveals Galactic cirrus clouds at low and intermediate velocities.

Load-bearing premise

The completeness and reliability claims assume that the residual image, created by subtracting the detected real sources from the mosaic, is a faithful stand-in for the true sky noise at faint fluxes, so that reinserted fake sources are detected and matched with the same probability as real faint sources.

Editorial extensions

If this is right

  • The public catalog gives a statistically characterized 24 micron sample over about five square degrees, enabling source counts, luminosity functions, and clustering measurements at flux levels between the IRAS survey and the deepest ISO fields.
  • Because more than 80% of sources have reliable optical counterparts down to R=25.5, the catalog supports direct construction of the optical-to-mid-infrared spectral energy distributions of the 24 micron selected population.
  • The residual map, separated from the point sources, exposes Galactic cirrus clouds at low and intermediate velocities, showing that foreground emission can be modeled and removed in this moderately high-latitude field.
  • The 16% of sources with 20 cm counterparts, combined with spectroscopic redshifts already available in the field, provide a clean subset for studying the mid-infrared to radio relation in star-forming galaxies and active galactic nuclei.
  • The published per-source position and flux errors as functions of SNR allow users to select subsamples with controlled astrometric and photometric quality, for instance SNR greater than 10 for roughly 10% flux accuracy.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • An implicit consequence is that the reinsertion-simulation technique could be generalized to produce a per-pixel completeness map rather than a single global curve; the released residual and coverage maps contain enough information to attempt this for any extragalactic survey.
  • The acknowledged bias toward high fluxes at SNR lower than 10 means that number counts derived from this catalog without a statistical correction will be slightly overestimated at the faint end; the published error curves provide the input needed to compute that correction.
  • The two survey depths (main and verification) on the same sky offer a controlled test: consistent source counts after completeness correction would independently validate the simulation-based completeness estimates.
  • The cirrus structures in the residual map, combined with the coverage map, could be used to quantify how foreground emission raises the local noise and reduces the effective depth across the field, a step the paper does not take.
Original abstract

We present the reduction of the 24 micron data obtained during the first cosmological survey performed by the Spitzer Space Telescope (First Look Survey, FLS). The survey consists of a shallow observation of 2.5x2 sq deg centered at 17h18m +59d30m (main survey) and a deeper observation of 1x0.5 sq deg centered at 17h17m +59d45m(verification survey). Issues with the reduction of the 24 micron MIPS data are discussed and solutions to attenuate instrumental effects are proposed and applied to the data. Approximately 17000 sources are extracted with a SNR greater than five. The photometry of the point sources is evaluated through PSF fitting using an empirical PSF derived from the data. Aperture corrections and the absolute calibration have been checked using stars in the field. Astrometric and photometric errors depend on the SNR of the source varying between 0.35-1 arcsec and 5-15%, respectively, for sources detected at 20-5 sigma. The flux of the 123 extended sources have been estimated through aperture photometry. The extended sources cover less than 0.3% of the total area of the survey. Based on simulations, the main and verification surveys are 50% complete at 0.3 and 0.15 mJy, respectively. Counterparts have been searched for in optical and radio catalogs. More than 80% of the 24 micron sources have a reliable optical counterpart down to R=25.5. 16% of the sources have a 20 cm counterpart down to 0.1 mJy and ~ 80% of the radio-infrared associations have a reliable optical counterpart. A residual map is obtained by subtracting point sources detected at the 3-sigma level and interpolating the regions occupied by extended sources. Several galactic clouds with low and intermediate velocities are identified by comparison with neutral Hydrogen data from this field.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 10,364 input tokens.

What the abstract itself states, as probabilities: claims first 0.32 · states limitation 0.67 · human participants 0.01 · controlled comparison 0.05 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.15 · mentions code or data availability 0.03.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

We present the reduction of the 24 micron data obtained during the first cosmological survey performed by the Spitzer Space Telescope (First Look Survey, FLS). The survey consists of a shallow observation of 2.5x2 sq deg centered at 17h18m +59d30m (main survey) and a deeper observation of 1x0.5 sq deg centered at 17h17m +59d45m(verification survey). Issues with the reduction of the 24 micron MIPS data are discussed and solutions to attenuate instrumental effects are proposed and applied to the data. Approximately 17000 sources are extracted with a SNR greater than five. The photometry of the point sources is evaluated through PSF fitting using an empirical PSF derived from the data. Aperture corrections and the absolute calibration have been checked using stars in the field. Astrometric and photometric errors depend on the SNR of the source varying between 0.35-1 arcsec and 5-15%, respectively, for sources detected at 20-5 sigma. The flux of the 123 extended sources have been estimated through aperture photometry. The extended sources cover less than 0.3% of the total area of the survey. Based on simulations, the main and verification surveys are 50% complete at 0.3 and 0.15 mJy, respectively. Counterparts have been searched for in optical and radio catalogs. More than 80% of the 24 micron sources have a reliable optical counterpart down to R=25.5. 16% of the sources have a 20 cm counterpart down to 0.1 mJy and ~ 80% of the radio-infrared associations have a reliable optical counterpart. A residual map is obtained by subtracting point sources detected at the 3-sigma level and interpolating the regions occupied by extended sources. Several galactic clouds with low and intermediate velocities are identified by comparison with neutral Hydrogen data from this field.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We present the reduction of the 24 micron data obtained during the first cosmological survey performed by the Spitzer Space Telescope (First Look Survey, FLS). contribution 1.00 0.94 0.09 asserted 0.99
s1 The survey consists of a shallow observation of 2.5x2 sq deg centered at 17h18m +59d30m (main survey) and a deeper observation of 1x0.5 sq deg centered at 17h17m +59d45m(verification survey). method 0.69 0.77 0.02 asserted 1.00
s2 Issues with the reduction of the 24 micron MIPS data are discussed and solutions to attenuate instrumental effects are proposed and applied to the data. method 0.88 0.90 0.06 asserted 0.99
s3 Approximately 17000 sources are extracted with a SNR greater than five. result 0.99 0.95 0.10 asserted 1.00
s4 The photometry of the point sources is evaluated through PSF fitting using an empirical PSF derived from the data. method 1.00 0.95 0.03 asserted 1.00
s5 Aperture corrections and the absolute calibration have been checked using stars in the field. method 0.98 0.93 0.03 asserted 1.00
s6 Astrometric and photometric errors depend on the SNR of the source varying between 0.35-1 arcsec and 5-15%, respectively, for sources detected at 20-5 sigma. result 1.00 0.92 0.05 asserted 1.00
s7 The flux of the 123 extended sources have been estimated through aperture photometry. method 0.64 0.96 0.04 asserted 1.00
s8 The extended sources cover less than 0.3% of the total area of the survey. result 1.00 0.90 0.03 asserted 1.00
s9 Based on simulations, the main and verification surveys are 50% complete at 0.3 and 0.15 mJy, respectively. result 0.98 0.81 0.08 asserted 0.99
s10 Counterparts have been searched for in optical and radio catalogs. method 0.86 0.92 0.03 asserted 0.98
s11 More than 80% of the 24 micron sources have a reliable optical counterpart down to R=25.5. 16% of the sources have a 20 cm counterpart down to 0.1 mJy and ~ 80% of the radio-infrared associations have a reliable optical counterpart. result 1.00 0.93 0.13 asserted 1.00
s12 A residual map is obtained by subtracting point sources detected at the 3-sigma level and interpolating the regions occupied by extended sources. method 0.90 0.95 0.03 asserted 1.00
s13 Several galactic clouds with low and intermediate velocities are identified by comparison with neutral Hydrogen data from this field. result 0.98 0.92 0.06 asserted 1.00

What kind of paper the classifier reports this is: dataset or benchmark 0.97 · evidence from analysis of existing data 0.53.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. — Coverage of public surveys in the FLS region. From the outside going toward the cen￾ter: (1) KPNO R-images (Fadda et al. 2004), (2) 24 µm main field (this paper), (3) VLA 20cm (Condon et al., 2003), (4) IRAC channels 1 and 3 (Lacy et al. 2005), (5) IRAC channels 2 and 4 (Lacy et al. 2005), (6) WSRT 20cm (Morganti et al. 2004), (7) 24 µm verification field (this pa￾per), (8) ACS/HST data (Storrie-Lombardi et al., in prep.). A region similar to the 24µm one has been covered also at 70µm and 160 µm (Frayer et al. 2005). The improvement of depth and quality of the mid-IR images with S
Figure 2. — Left: A typical LIRG (LIR = 1011L⊙) as seen at three different redshifts by different Spitzer detectors (SED of M82 renormalized). Right: 24µm flux of the same galaxy with different luminosities as a function of the redshift. Horizontal bars show the sensitivity limits of the main and verification survey. In the verification region, LIRGs can be detected up to a redshift of 2.5. in prep.) 1 . Moreover, the field has been observed in i’ and g’ with the 200in Palomar LFC camera (Glassman et al., in prep.), u’ and g’ with the CFH Megacam (Shim et al., 2006), in J and Ks with…
Figure 3. — Median flux shift of pixels read by the
Figure 4. — Scan-mirror angle versus y-pixel coor
Figure 6. — Long term drift in the median flux as a
Figure 7. — The effect of corrections on the median value of the frames o
Figure 8. — Offsets of groups of 25 images with the same telescope pointing along the in-scan and cross-scan directions in arcseconds with respect to the r’ image of the field obtained by the SDSS. The bottom panel reports the number of sources with optical counterpart in each image used for computing the offsets. The grey and white back￾ground separates the different AORs. As a reference image we used the SDSS r’ image of the field. This observation has the advantage of having accurate astrometry (error < 0.1 arcsec) covering the entire field and to be sufficiently deep to find a high number…
Figure 9. — Left: coverage map of the MIPS24 observations. Right: the differential (top) and cumulative (bottom) plots of the coverage versus area. The two vertical dotted lines mark the median coverage in the main and verification surveys. Although the SSC pipeline provides a mask of bad pixels which are damaged or saturated, several other pixels have to be masked because of cosmic rays. Among the several possibilities offered by MOPEX to detect these pixels, we choose the most conservative one which relies on redundancy. As visible in
Figure 10. — Theoretical (left) and empirical (center) PRF evaluated b
Figure 11. — Ratio between peak and 5” aperture fluxes. Points higher than the 3-σ errorband are candidate extended sources. The triangles are the extended sources found with run bright detect module. The points encircled appear extended in the optical images. The two negative outliers cor￾respond to two sources on the border for which the aperture misses part of the flux. aperture flux is affected by the companion source. Usually, sources within this distance have been de￾blended by the extraction algorithm used or have been already identified as extended sources with the run bright detect…
Figure 13. — Completeness and reliability of the extracted sources at th
Figure 14. — Difference between true and estimated fluxes versus SNR for sources detected in the sim￾ulation. Points correspond to the sources. The big dots correspond to the median difference. The two lines mark the 1σ error band. The error in￾creases towards low SNR values. Moreover, at low SNR values the estimated fluxes are biased to￾wards higher values since sources on positive fluc￾tuations of the noise are preferentially detected. residual image. In particular, we divided the im￾age in two regions according to the coverage: (a) coverage greater than 37 images (roughly corre￾sponding to…
Figure 16. — Left: distance between true and estimated positions vers
Figure 17. — From left to right, the image before and after the latency c
Figure 18. — Azimuthally-averaged profile normal￾ized to the total flux of the source. Line and dots correspond to the synthetic and real source, re￾spectively. The first three Airy rings are clearly visible. Error bars correspond to the 1-σ disper￾sion of fluxes inside the annulus. The shaded re￾gion corresponds to the same 1-σ dispersion for the synthetic star. for instance, those in the SWIRE fields (Lonsdale et al. 2003). We remind that, in the case of source extrac￾tion, we were able to follow such a procedure. In fact, since in this case we consider only the part inside the first Airy…
Figure 19. — Left: calibration factor versus predicted flux for 24µm stars in the FLS with SDSS, 2MASS and IRAC counterparts. The point in the bottom-right corner indicates the typical errorbar. The empty circles are stars with possible excess of infrared emission not considered in our analysis. Right: relationship between predicted and measured values of the flux for the 224 stars marked with full circles on the left plot. The value found is less than 0.5% higher than the official 24µm Spitzer calibration value (see horizontal line on the left plot). One-sigma errorbars are reported on the…
Figure 20. — Color correction as function of the red
Figure 21. — Cirrus foreground at 24 µm compared with the HI maps of Lockman & Condon (2005). North is up and East is left. Left: low velocity clouds ( -4.7< V < 0.7 km/s) with NHI contours corresponding to 0.16, 0.2 and 0.3 1020cm−2 . Right: intermediate velocity clouds (-35 < V < -45 km/s) with NHI contours corresponding to 0.87, 1.2 and 1.5 1020cm−2 . point sources have extended radio sources as coun￾terparts. We matched in the same way the ex￾tended source catalog, finding counterparts for 53% of the 94 sources inside the VLA field. The radio-infrared associations are given in the point…
Figure 22. — Magnitude distribution of possible counterparts (solid line) and background objects (dotted line) within a 2 arcsec radius from each 24µm source. The solid curve has been normal￾ized according to equation (10) and used in the Likelihood Ratio definition. with b the surface density of background objects at magnitude m. The reliability of an association with the i-th candidate is defined as: Ri = P Li j Lj + (1 − G) , (8) where the sum is done over the set of all possible candidates and G is the probability that the can￾didate is brighter than the magnitude limit of the catalog (

Showing 19 of the paper's 22 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:astro-ph/0603488 by the authors.

References
How the literature uses it

1 arXiv paper cite this in 1 sentence

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it

Uses its data or values 1 paper
  • 26.3 MHz 2 [ref] 26.3 MHz–14.9 GHz 9 [ref] 28.6 MHz–10.7 GHz 74 [ref] 38 MHz–5 GHz 12 [ref] 60 MHz 1 [ref] 80–160 MHz 2 [ref] 111 MHz 1 [ref] 151 Mhz–8.48 GHz 8 [ref] 178 MHz 18 [ref] 178 MHz 4 [ref] 324 MHz–95 GHz 8 [ref] 408 MHz 1 [ref] 610 MHz 2 [ref] 750 MHz–1.4 GHz 6 [ref] 966 MHz 9 [ref] 1.28 GHz 1 [ref] 1.38–22 GHz 23 [ref] 1.38–90 GHz 5 [ref] 1.4 GHz 14 [ref] 1.4 GHz 4 [ref] 1.4 GHz 1 [ref] 1.4 GHz 1 [ref] 1.4 GHz 1 [ref] 1.4 GHz 1 [ref] 1.4 GHz 2 [ref] 1.4 GHz 4 [ref] 1.4–8.3 GHz 16 [ref] 1.4–43 GHz 35 [ref] 1.41 GHz 13 [ref] 1.42 GHz 1 [ref] 1.46–22.5 GHz 63 [ref] 1.47–4.71 GHz 4 [ref] 1.48–90 GHz 46 [ref] 1.6–5 GHz 4 [ref] 1.63 GHz 1 [ref] 2.7 GHz 3 [ref] 2.7–8.1 GHz 2 [ref] 2.7–10.7 GHz 19 [ref] 4.58–90 GHz 16 [ref] 4.75 GHz 1 [ref] 4.8 GHz 4 [ref] 4.8 GHz 4 [ref] 4.8 GHz 4 [ref] 4.8–5 GHz 21 [ref] 4.8–14.5 GHz 3 [ref] 4.8–14.5 GHz 6 [ref] 4.8–15 GHz 4 [ref] 4.8–22.2 GHz 4 [r

    Simulations and Observations of the Microwave Universe · Radio cameras · 0.99

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