--- title: 'GOODS-ALMA 2.0: Wide-Field Dust Continuum Survey' url: https://www.emergentmind.com/topics/goods-alma-2-0-survey type: topic --- # GOODS-ALMA 2.0: Wide-Field Dust Continuum Survey Searching arXiv for GOODS-ALMA 2.0 and ASAGAO papers to ground the article in the relevant literature. GOODS-ALMA 2.0 is a blind ALMA Band 6 continuum survey of the GOODS-South field designed to obtain a homogeneous, contiguous census of dust-obscured star formation at 1.1 mm over cosmic noon and beyond. In the GOODS-ALMA 2.0 formulation, the survey covers a continuous area of 72.42 arcmin\(^2\) in GOODS-South with combined high-resolution and low-resolution observations, yielding a synthesized beam of \(0.447'' \times 0.418''\) and an average point-source sensitivity of \(\sigma_{1.1\,\mathrm{mm}} = 68.4\,\mu\mathrm{Jy}\,\mathrm{beam}^{-1}\) [2106.13246]. Closely related work on the ASAGAO program, sometimes described as a GOODS-ALMA 2.0 survey in the 1.2 mm context, provides a complementary 26 arcmin\(^2\) GOODS-South map with different survey geometry, depth, and science emphasis, including source counts, luminosity functions, and resolved morphology [1808.04502; 1802.02136]. Across these studies, GOODS-ALMA 2.0 denotes a transition from small-area or single-configuration millimeter surveys to a wide, uniform, multi-configuration framework for measuring source demographics, dust-continuum sizes, star-formation compactness, and the role of obscured systems in galaxy evolution. ## 1. Survey definition and observational architecture GOODS-ALMA 2.0 is a blind 1.1 mm continuum survey covering 72.42 arcmin\(^2\) in the GOODS-South field, defined at primary beam \(\ge 20\%\) [2201.02633; 2106.13246]. The field center is given as \(\mathrm{RA} = 03^\mathrm{h}\,32^\mathrm{m}\,30^\mathrm{s}\), \(\mathrm{Dec} = -27^\circ\,48'\,00''\) [2201.02633]. The survey combines two ALMA Band 6 configurations in order to improve \(uv\)-coverage and recover both compact and extended emission [2106.13246]. The high-resolution component, identified with GOODS-ALMA 1.0, used Cycle 3 observations with baselines \(16.7\,\mathrm{m}/1808\,\mathrm{m}\), a synthesized beam of \(0.251'' \times 0.232''\), and rms \(\simeq 89\,\mu\mathrm{Jy}\,\mathrm{beam}^{-1}\) [2201.02633; 2106.13246]. The low-resolution component used Cycle 5 observations with baselines \(15.0\,\mathrm{m}/360.5\,\mathrm{m}\), a beam of \(1.33'' \times 0.935''\), and rms \(\simeq 95\,\mu\mathrm{Jy}\,\mathrm{beam}^{-1}\) [2201.02633; 2106.13246]. The combined dataset reaches a beam of \(0.447'' \times 0.418''\) and average sensitivity \(\sigma = 68.4\,\mu\mathrm{Jy}\,\mathrm{beam}^{-1}\) [2106.13246]. Each dataset is described as an 846-pointing mosaic with total on-source time \(\approx 14\,\mathrm{h}\) per configuration [2106.13246]. The full \(uv\)-coverage, \(15\text{--}1808\,\mathrm{m}\), was obtained by concatenating calibrated visibilities in CASA v5.6.1, and the continuum was imaged with TCLEAN using a dirty map and natural weighting, specifically to avoid beam-mismatch systematics when combining configurations [2106.13246]. A related but distinct GOODS-South ALMA survey, ASAGAO, mapped a contiguous \(5' \times 5'\) region, corresponding to \(\approx 26\) arcmin\(^2\), at 1.2 mm in Band 6 with two tunings centered at 262.56 GHz and 253.56 GHz [1808.04502]. Its inclusion is important because several later GOODS-South analyses treat ASAGAO as part of the broader GOODS-ALMA 2.0 landscape, especially for source statistics and dusty-galaxy morphology. This suggests that the nomenclature around “GOODS-ALMA 2.0” has both a strict 1.1 mm definition and a broader GOODS-South ALMA survey context. ## 2. Detection strategy, catalog construction, and counterpart identification The GOODS-ALMA 2.0 source catalog was built from a blind search on the combined dirty map using PyBDSF [2106.13246]. Detection thresholds were explored with pixel threshold \(\sigma_p\) from 3.0 to 6.0 and island threshold \(\sigma_f = 2.7\), with one Gaussian per blob and \(S/N_{\rm peak}\) defined as \[ S/N_{\rm peak} = S_{\rm peak} / \sigma_{\rm rms}. \] Negative-image tests yielded \(p=1\) for \(\sigma_p \ge 4.4\) in the combined map, corresponding to 100% purity [2106.13246]. On that basis, 44 100%-pure sources with \(S/N_{\rm peak} \ge 5\) define the main catalog [2106.13246]. A supplementary prior-based catalog extends the sample below the pure blind threshold. Running blind detection down to \(\sigma_p = 3.0\) yields \(\sim 98\) real sources, and 44 new candidates with \(3.5 \le S/N_{\rm peak} < 5\) were validated by IRAC (3.6/4.5 \(\mu\mathrm{m}\)) or VLA (3 GHz) priors within \(0.4''\) and stellar mass \(M_\star \ge 10^9\,M_\odot\) [2106.13246]. The total GOODS-ALMA 2.0 catalog therefore contains 88 galaxies, split evenly between the main and supplementary components [2106.13246; 2201.02633]. The catalog composition is summarized concisely below. | Component | Selection | Number of sources | |---|---|---:| | Main catalog | \(S/N_{\rm peak} \ge 5\), 100% pure | 44 | | Supplementary catalog | \(3.5 \le S/N_{\rm peak} < 5\), aided by priors | 44 | | Total | Combined GOODS-ALMA 2.0 catalog | 88 | Among the 88 sources, 13 are optically dark or faint, specifically \(H\)- or \(K\)-band dropouts [2106.13246]. The final sample has median redshift \(z \approx 2.46\), spanning \(0.1 \lesssim z \lesssim 5\), and a subset of 69 sources has Herschel detections [2201.02633]. In the supplementary analysis of faint GOODS-ALMA detections, 16 additional \(3.5\text{--}4.8\,\sigma\) galaxies were identified in the 1.1 mm field using IRAC and VLA priors, including two galaxies undetected in HST/WFC3 \(H\)-band imaging to \(5\sigma \approx 28.2\) AB [2005.03040]. That work also showed that the publicly released HST positions required both a global astrometric correction and a local distortion correction for reliable multiwavelength associations [2005.03040]. The ASAGAO 1.2 mm catalog construction followed a different workflow. Source extraction on the \(250\,k\lambda\)-tapered map found 25 sources at \(\ge 5.0\sigma\) and 45 at \(\ge 4.5\sigma\), with spurious fractions estimated from negative peaks and completeness calibrated through 30,000 Monte Carlo point-source injections [1808.04502]. Optical and near-infrared counterpart matching used the ZFOURGE catalog after applying an astrometric correction of \((-0.086'', +0.282'')\) for Gaia DR1 tie-in, and 88% of \(5\sigma\) sources had secure optical/IR/radio counterparts [1808.04502]. ## 3. Imaging products, fluxes, sizes, and morphological methodology GOODS-ALMA 2.0 was explicitly designed to mitigate the common limitations of earlier millimeter surveys: discontinuous sky coverage, inhomogeneous sensitivity, and modest \(uv\)-coverage from single-array observations [2106.13246]. Its combined configuration permits robust characterization of both unresolved and resolved dust emission, with source sizes measured in the \(uv\)-plane via UVMODELFIT using a circular Gaussian model [2106.13246; 2201.02633]. Fluxes were measured with 1.6''-diameter aperture photometry plus aperture correction from the local synthesized beam [2106.13246]. A source is considered unresolved when the fitted \(R_e\) falls below the Martí-Vidal et al. minimum resolvable size, \[ \theta_{\min} \simeq 0.88\,\theta_{\rm beam}/\sqrt{S/N}, \] and the effective radius is derived from the Gaussian FWHM as \[ R_e = \mathrm{FWHM}/2\sqrt{\ln 2}. \] These definitions are central to the survey’s compactness analysis [2106.13246]. For the main catalog, the median dust-continuum effective radius is \(R_e = 0.10'' \pm 0.05''\), corresponding to \(0.73 \pm 0.29\) kpc [2106.13246; 2201.02633]. The high-resolution subset has \(R_e = 0.09'' \pm 0.03''\) or \(0.70 \pm 0.23\) kpc, while low-resolution-only detections have \(R_e = 0.15'' \pm 0.10''\) or \(1.21 \pm 0.82\) kpc [2106.13246]. For sources with \(S_{1.1\,\mathrm{mm}} > 1\) mJy, compact emission is described as prevailing, and sizes as extended as typical star-forming stellar disks are reported to be rare [2106.13246]. The survey also quantified scaling behavior with redshift and stellar mass. Stacks above and below \(z_{\rm med} = 2.46\) and \(M_\star = 10^{10.79}\,M_\odot\) gave \[ R_e \propto M_\star^\alpha \quad \text{with} \quad \alpha \approx 0.11, \] and \[ R_e \propto (1+z)^\beta \quad \text{with} \quad \beta \approx -0.53, \] at fixed redshift and fixed mass, respectively [2106.13246]. These trends resemble the stellar-size evolution of late-type galaxies from optical measurements, but with \(\approx 30\%\text{--}50\%\) lower normalization [2106.13246]. ASAGAO extended morphological analysis beyond simple Gaussian sizes by fitting Sérsic profiles to stacked 1.2 mm emission. Using visibility stacking on 33 ASAGAO objects at \(z=1\text{--}3\), followed by Monte Carlo centering-error correction, the survey obtained \[ n_{\rm FIR} = 1.2 \pm 0.2,\qquad R_{e,\rm FIR} = 0.12'' \pm 0.03'' \rightarrow 1.0 \pm 0.2\,\mathrm{kpc} \] at \(z_{\rm med} = 2.00\) [1802.02136]. In the rest-frame optical, 21 ASAGAO galaxies cross-matched to the van der Wel et al. HST catalog gave median \[ n_{\rm opt} = 0.9 \pm 0.3,\qquad R_{e,\rm opt} = 3.2 \pm 0.6\,\mathrm{kpc}, \] supporting the interpretation that the FIR-emitting disk is embedded within a larger stellar disk [1802.02136]. ASAGAO also found that two-component fits preferred a point source plus disk over bulge plus disk, with the point source contributing \(1.5 \pm 0.5\%\) of the total 1.2 mm flux, interpreted as an AGN candidate [1802.02136]. ## 4. Number counts, resolved background light, and luminosity functions A major objective of GOODS-ALMA 2.0 and ASAGAO is to quantify the faint millimeter-source population and its contribution to the cosmic infrared background and obscured star-formation history. In GOODS-ALMA 2.0, the per-source contribution to number counts is written as \[ \xi(S_i) = \frac{p(S_i^{\rm peak})}{A_{\rm eff}(S_i^{\rm peak})\,C(S_i,\theta)}, \] with purity, effective area, and completeness explicitly incorporated [2106.13246]. Completeness was calibrated through Monte Carlo injections over 30 fluxes and 11 sizes, yielding nearly 100% completeness for \(S_{1.1\,\mathrm{mm}} > 1\) mJy and lower completeness toward faint, extended sources [2106.13246]. Effective area from the combined noise map reached 100% area at \(\ge 83.5\,\mu\mathrm{Jy}\) and 90% at \(\ge 71.7\,\mu\mathrm{Jy}\) [2106.13246]. The differential number counts span \(0.3\text{--}3\) mJy and are reported to be in good agreement with other ALMA studies [2106.13246]. A Schechter function fit, \[ \phi(S) = \frac{N_0}{S_0}(S/S_0)^\alpha \exp(-S/S_0), \] gives \[ N_0 = 2290^{+370}_{-330}\,\mathrm{deg}^{-2},\quad S_0 = 1.89^{+0.17}_{-0.10}\,\mathrm{mJy},\quad \alpha = -1.97^{+0.05}_{-0.03} \] for the differential counts [2106.13246]. Integrating to \(S > 0.3\) mJy yields \[ I_\nu = 0.0289^{+0.0011}_{-0.0006}\,\mathrm{MJy}\,\mathrm{sr}^{-1}, \] corresponding to \(\sim 38\%\) of the COBE CIB at 1.13 mm [2106.13246]. ASAGAO derived independent number counts at 1.2 mm using completeness- and reliability-corrected source weights, \[ \frac{dN}{dS} = \frac{1}{\Delta S}\sum_i\frac{1-f_{\rm neg}(\mathrm{SN}_i)}{A(S_i)\,C(\mathrm{SN}_i)}, \] and fitted the combined ALMA counts with a Schechter form characterized by \[ N' = (31.3\pm16.6)\times10^2\,\mathrm{deg}^{-2},\quad S' = 1.34\pm0.30\,\mathrm{mJy},\quad \alpha = -2.03\pm0.16 \] [1808.04502]. Integrating from \(S_{\rm lim} = 135\,\mu\mathrm{Jy}\), ASAGAO found \[ I_{\rm resolved} = 7.7^{+1.7}_{-1.2}\,\mathrm{Jy}\,\mathrm{deg}^{-2}, \] and, relative to Planck’s \(I_{\rm EBL} = 15.1\pm0.6\,\mathrm{Jy}\,\mathrm{deg}^{-2}\), obtained \[ f_{\rm EBL}(>135\,\mu\mathrm{Jy}) = 52^{+11}_{-8}\%. \] This result places a quantitative lower bound on the fraction of the 1.2 mm background resolved into discrete sources [1808.04502]. ASAGAO additionally constructed infrared luminosity functions in the redshift range \(z=1\text{--}3\) using the \(V_{\max}\) method. At \(1.511.0\), \(19/32\), or \(\approx 59\%\), are classified as starbursts in the main sequence [2201.02633]. The role of compactness is explicit. The star-forming area is defined as \(\pi R_e(1.1\,\mathrm{mm})^2\), and an optical comparison area \(A_{\rm opt}\) is defined from the expected optical disk area at the galaxy’s \(M_\star\) and \(z\) [2201.02633]. At fixed mass and redshift, increasing compactness of the 1.1 mm emission relative to the optical disk, expressed as larger \(A_{\rm opt}/A_{\rm mm}\), correlates with lower \(\tau_{\rm dep}\), lower \(f_{\rm gas}\), and higher \(T_{\rm dust}\), with Spearman \(p<0.5\%\) [2201.02633]. Starbursts in the main sequence occupy the extreme of these relations [2201.02633]. Stacked visibilities reinforce the compactness contrast. The \(uv\)-stack of the 23 starbursts in the main sequence yields \(R_{e,\rm stack} \approx 0.52 \pm 0.05\) kpc after correction to the median sample \(M_\star = 10^{10.79}\,M_\odot\), \(z = 2.46\), whereas the remaining main-sequence galaxies stack to \(R_e \approx 0.99 \pm 0.06\) kpc [2201.02633]. This difference links the survey’s size measurements directly to physical regulation of star formation. A related mass-selected analysis based on ASAGAO and ZFOURGE found that ALMA-detected ZFOURGE galaxies at median redshift \(z_{\rm median} = 2.38 \pm 0.14\) generally follow the star-forming main sequence, but exhibit systematically larger infrared excess, \(\mathrm{IRX} \equiv L_{\rm IR}/L_{\rm UV}\), than K-selected galaxies without ALMA detections even at similar redshifts, masses, and star formation rates [2005.13346]. This implies that the consensus stellar-mass versus IRX relation from rest-frame-UV-selected galaxies cannot fully predict ALMA detectability in stellar-mass-selected samples [2005.13346]. ## 6. Evolutionary interpretation, star-formation histories, and links to quenching The GOODS-ALMA 2.0 dataset has been used to test whether compact dusty systems are transient post-starburst objects or a structurally distinct component within the main sequence. Using CIGALE v2022.1 with non-parametric star-formation histories implemented through the “sfhNlevels” module, the last gigayear SFHs of 65 GOODS-ALMA galaxies with full UV–mm coverage were reconstructed in seven logarithmically spaced lookback-time bins [2211.02510]. To quantify recent evolutionary direction in the SFR–\(M_\star\) plane, the analysis defined the SFR gradient \(\nabla\mathrm{SFR}(t)\) as the angle between the evolutionary vector and the horizontal axis: \[ \nabla\mathrm{SFR} = \arctan2[\Delta\log\mathrm{SFR},\,\Delta\log M_\star] = \arctan\left( \frac{\log\mathrm{SFR}_0-\log\mathrm{SFR}_{\Delta t}} {\log M_{\star,0}-\log M_{\star,\Delta t}} \right). \] Values near \(0^\circ\) indicate constant specific SFR, \(+90^\circ\) a strong recent starburst, and \(-90^\circ\) rapid recent quenching [2211.02510]. For the 14 starbursts in the main sequence and 51 normal main-sequence GOODS-ALMA galaxies, the median SFR gradients are similar over 100 Myr, 300 Myr, and 1 Gyr. At 100 Myr, the medians are \(+12^\circ\) for normal main-sequence galaxies and \(+15^\circ\) for starbursts in the main sequence; at 300 Myr, \(+25^\circ\) and \(+28^\circ\); and at 1000 Myr, \(+43^\circ\) and \(+48^\circ\), respectively [2211.02510]. No starburst-in-the-main-sequence galaxy shows \(\nabla\mathrm{SFR} < -50^\circ\) over any interval [2211.02510]. The two distributions are statistically indistinguishable, with KS \(p \gg 0.1\) [2211.02510]. These results were used to evaluate three scenarios. A compaction scenario involving violent inflow to the top of the main sequence was argued to be disfavored because starbursts in the main sequence show low gas fractions and no past high-burst signature. A post-starburst passage through the main sequence was argued to be ruled out by the absence of large negative \(\nabla\mathrm{SFR}\). A “mild compaction/feeding within the MS” scenario, in which centrally concentrated star formation builds compact cores while galaxies remain inside the main sequence, was supported by the positive or flat gradients [2211.02510]. This suggests that main-sequence scatter contains structurally heterogeneous galaxies with similar self-regulated recent growth. The ASAGAO morphology analysis points in a compatible direction. The radial surface-density profile of the total SFR, built from stacked HST/F606W and ALMA data, shows that \(\Sigma_{\rm SFR,IR}\) dominates over \(\Sigma_{\rm SFR,UV}\) at \(r<1\) kpc, indicating a heavily dust-enshrouded central kiloparsec [1802.02136]. Under a constant-SFR assumption over either the gas-depletion time \(\sim 0.2\text{--}0.6\) Gyr or the cosmic interval \(\Delta t \approx 1\) Gyr from \(z=2 \rightarrow 1.5\), the shrinkage of \(R_{e,\rm opt}\) toward values typical of compact quiescent galaxies can be reproduced, but the transformation from \(n_{\rm opt} \approx 1\) to \(n_{\rm opt} = 4\) cannot [1802.02136]. The stated implication is that additional dynamical processes, such as dissipation or merging, are required to build the spheroidal stellar profiles of \(z \approx 1\text{--}2\) quiescent galaxies [1802.02136]. A later JWST+ALMA analysis of 33 GOODS-ALMA 2.0 galaxies at \(z=1.5\text{--}5.5\) extends this interpretation. It reports that the 1.1 mm-selected sample shows a \(2.6\times\) steeper decrease of size with increasing wavelength than the field star-forming population, and that at 4.4 \(\mu\mathrm{m}\) these galaxies align with the quiescent size–mass locus rather than the field star-forming one [2507.19472]. The rest-NIR surface-brightness profiles are described as remarkably similar to those of quiescent galaxies in the inner regions, which was interpreted as evidence that dusty star-forming galaxies have already built up stellar mass in a severely dust-obscured core [2507.19472]. This suggests a strong evolutionary connection between compact dusty systems and subsequent quiescent descendants. ## 7. Scientific significance, scope, and common points of confusion The scientific significance of GOODS-ALMA 2.0 lies in the combination of contiguous area, homogeneous sensitivity, two-configuration \(uv\)-coverage, and the integration of deep ancillary data in GOODS-South. The survey increased the sample size of robust millimeter detections from the earlier high-resolution-only census to 88 galaxies and established that 1.1 mm dust emission is generally compact, with a median \(R_e\) of \(0.73 \pm 0.29\) kpc [2106.13246]. For bright sources with \(S_{1.1\,\mathrm{mm}} > 1\) mJy, it concluded that compact dust continuum emission prevails and that dust disks as large as typical star-forming stellar disks are rare [2106.13246]. At the population level, the survey showed that optically dark or faint sources form a non-negligible component of the millimeter-selected sample, with 13 such objects in the 88-source catalog [2106.13246]. The supplementary prior-assisted GOODS-ALMA work similarly found that lowering the threshold with robust multiwavelength priors reveals galaxies that are, on average, twice as large in the FIR and of lower stellar mass than the original main-catalog sample, while still remaining significantly more compact in the FIR than in the optical [2005.03040]. This indicates that compact dusty star formation is not restricted to the most extreme bright submillimeter galaxies. A recurrent point of confusion concerns the relationship between GOODS-ALMA 2.0 and ASAGAO. The strict GOODS-ALMA 2.0 survey is the blind 1.1 mm GOODS-South program covering 72.42 arcmin\(^2\) with two array configurations [2106.13246; 2201.02633]. ASAGAO, by contrast, is a 1.2 mm ALMA Band 6 survey over 26 arcmin\(^2\) in GOODS-South, with its own catalog, source counts, and morphological analysis [1808.04502; 1802.02136]. The surveys are scientifically adjacent rather than identical. Their results are nevertheless strongly complementary: both find compact dust-obscured star formation, both operate in GOODS-South with extensive ancillary data, and both support the view that obscured star formation is centrally concentrated relative to the stellar distribution. Another important interpretive issue is whether compact dusty galaxies are simply merger-driven outliers above the main sequence. GOODS-ALMA 2.0 does not support a single, universal answer. A substantial fraction of its galaxies lie within the main sequence scatter despite short depletion times, low gas fractions, high dust temperatures, and compact star-forming regions [2201.02633]. The SFH analysis further argues that these “starbursts in the main sequence” are not obviously fading post-starbursts, but systems with recent evolution similar to other main-sequence galaxies [2211.02510]. A plausible implication is that compact star formation can be a long-lived or recurrent mode of self-regulated growth rather than only a brief excursion. Taken together, GOODS-ALMA 2.0 and the associated GOODS-South ALMA analyses provide a benchmark empirical framework for studying dusty star-forming galaxies from source detection and number counts to structural evolution and pre-quenching physics. Their central result is not merely that millimeter-selected galaxies are dusty, but that the dust-obscured star formation itself is systematically compact, physically consequential, and tightly linked to the assembly of dense central stellar structures [2106.13246; 2201.02633; 1802.02136; 2507.19472]. Source: https://www.emergentmind.com/topics/goods-alma-2-0-survey