arXiv subjects

N. N. Geesink

Publications and source records attributed to N. N. Geesink.

5 recordsLinked to original sources

arXiv2026

ALMA Chemical Evolution (ACE) survey: The gas fundamental metallicity relation at cosmic noon

Chemical enrichment shapes how galaxies form and evolve. The gas-phase metallicity is directly linked to the stellar mass, star formation rate, and cold gas of the interstellar medium. Thus, the cold gas fundamental metallicity relation (GFMR) is a powerful tool for probing galaxy evolution, bridging large-scale gas flows modulating the cold gas reservoir and small-scale metal enrichment tracing the cumulative impact of star formation. Constraining all these properties for the same representative sample of galaxies remains challenging yet essential. Using CO(3--2) band 3 observations from the Atacama Large Millimeter/submillimeter Array Chemical Evolution (ACE) survey, we investigated the GFMR in a sample of 26 main-sequence (log(M_*, med)=9.96), subsolar-metallicity (12+log(O/H)_med=8.44) star-forming galaxies (SFGs) at z~2. With 17/26 CO detections, including some of the lowest-metallicity CO detections at cosmic noon, we find that the stellar mass remains the primary driver of the chemical evolution in our sample (sigmaMZR~0.10). Whereas the molecular gas likely plays a secondary role (sigmaGFMR~0.11) similar to that of the star formation rate (sigmaFMR~0.13). This likely reflects our sensitivity to only the CO-bright component of the molecular reservoir. Our results remain consistent with gas-regulator models and suggest the existence of efficient molecular outflows, with an average mass loading factor of eta~4, regulating star formation and chemical enrichment.

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arXiv2026

ALMA Chemical Evolution (ACE) survey: dust-to-gas ratios in sub-solar metallicity galaxies at cosmic noon

Dust is a fundamental component of the interstellar medium and provides a key tracer of the baryon cycle that regulates galaxy evolution. The dust-to-gas ratio links metals in the gas phase to those locked into dust grains, making it a sensitive diagnostic of dust production, grain growth, and destruction. We present measurements of the dust-to-molecular-gas ratio ($\rm DGR_{mol}$), for typical star-forming galaxies ($\log M_\star \approx 10$) at sub-solar metallicites, at $z\simeq2-2.5$ from the ALMA Chemical Evolution (ACE) survey. By combining ALMA CO and dust-continuum observations with robust gas-phase metallicity measurements, ACE extends direct dust and molecular-gas measurements to lower stellar masses and lower metallicities than previously available at this epoch, reaching down to $0.4\,Z_{\odot}$. This enables the first constraints on the $\rm DGR_{mol}$--metallicity relation for typical unlensed galaxies at cosmic noon. We find that $\rm DGR_{mol}$ increases with metallicity, with a log-space slope of $1.2 \pm 0.7$, indicating that metal-poor galaxies have systematically lower $\rm DGR_{mol}$ than their more metal-rich counterparts. For the detected ACE galaxies, we measure a mean value of $\log_{10}(M_{\rm dust}/M_{\rm mol})=-2.37\pm0.05$ for a mean metallicity of 12+$\log (\rm O/H) = 8.45 \pm 0.02$. We find agreement with $\rm DGR_{mol}$ in the local Universe at fixed metallicities, indicating that the same dust-growth physics, likely grain growth in the ISM, dominates at metallicities of $8.3 \leq 12+\log(\rm O/H) \leq 8.7$ at cosmic noon. These measurements provide novel empirical constraints for models of dust enrichment and galaxy evolution during the peak epoch of cosmic star formation. Additionally, ACE provides a sub-solar metallicity reference for the calibration of dust continuum as tracer of molecular gas, essential for studying metal-poor, high-redshift systems.

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arXiv2026

ALMA Chemical Evolution (ACE) survey: the dust content of subsolar metallicity galaxies at cosmic noon

Dust plays a key role in galaxy evolution by influencing star formation and shaping the observed spectrum of galaxies. However, at z~2 (cosmic noon) our knowledge of the dust mass budget is currently limited to the most massive, metal-rich systems, which are not representative of the bulk galaxy population. Here, we probe the lower mass, subsolar metallicity regime by measuring the dust mass of 25 galaxies at z~2.3 from the ALMA Chemical Evolution (ACE) Large Program. The sample contains star-forming galaxies in the COSMOS field with robust strong-line metallicities down to ~0.3 $Z_\odot$. Using the dust continuum emission detected at 873micron or 1.3mm we constrain the dust mass by assuming an optically thin single-temperature modified blackbody. The resulting dust masses average $10^{8}\,\mathrm{M}_\odot$, and they are three to nine times larger than those of z=0 galaxies at a matched metallicity and stellar mass. We also find positive correlations between dust mass and stellar mass, metallicity, and star formation rate (SFR). In contrast, we find that the $M_\mathrm{dust}/M_\mathrm{stars}$ (DtS) ratio scatters around $10^{-2.2}$ but shows no evidence of correlation with metallicity. This result is consistent with dust evolution models that predict a constant DtS once the ISM reaches the critical metallicity, at which metal accretion onto grains becomes the main mode of dust buildup. The correlation between $M_\mathrm{dust}/\mathrm{SFR}$ and metallicity also suggest that ACE galaxies have already surpassed the critical metallicity. Finally, we find that the DtS ratio is correlated to the specific SFR (sSFR). Since the sSFR are high ($> 10^{-8}\,\mathrm{yr}^{-1}$) this explains the DtS excess over z~0 galaxies. In turn, both sSFR and DtS are likely driven by the molecular gas fraction, as supported by CO(3-2) measurements taken as part of ACE.

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arXiv2026

Resolved SED Modeling with JWST and ALMA: The Role of Stellar Mass Surface Density in Regulating Star Formation in Cosmic Noon Galaxies

We present kpc-scale ($0.2''-0.5''$) physical property maps of 35 main-sequence galaxies at $z \approx 0.5-3.7$, with stellar masses of $\log(M_*/M_\odot) \sim 9.7-11.7$ and star formation rates of $\mathrm{SFR} \sim 1.4-280\,\mathrm{M_\odot\,yr^{-1}}$, selected from the ALMA Spectroscopic Survey (ASPECS) in the Hubble Ultra Deep Field. Leveraging the unique HST, JWST (NIRCam and MIRI), and ALMA observations, we perform spatially resolved spectral energy distribution (SED) modeling across the UV-to-FIR regime. We find that incorporating MIRI and/or ALMA data reduces the overestimation of dust luminosity (by up to $\sim0.8$ dex), while ALMA observations further mitigate the age-dust degeneracy. In the absence of such data, restricting the SED model library based on the observed unresolved colors can partially mitigate these biases. The stellar masses ($M_{*}$) derived from resolved and unresolved modeling are consistent within $\sim0.05$ dex, suggesting that mass discrepancies (attributed to outshining) are less significant for cosmic noon main-sequence galaxies when rest-frame near-infrared (NIR; e.g., $\sim1-3\,μ\mathrm{m}$) data are included. After normalization to the same reference, the composite SED of our sample closely resembles that of local starburst galaxies such as M82, suggesting similar dust attenuation and re-emission properties. Finally, we find that the molecular gas fraction and depletion time correlate with the effective stellar mass surface density ($Σ_{\rm eff,*} = M_{*}/2πR_{\rm eff,M_*}^2$) similarly to that observed in local galaxies. These results provide a first qualitative view of how the stellar gravitational potential influences gas regulation and star formation in galaxies beyond the local Universe.

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arXiv2025

PRUSSIC III -- ALMA and NOEMA survey of dense gas in high-redshift star-forming galaxies

Characterising the relationship between dense gas and star formation is critical for understanding the assembly of galaxies throughout cosmic history. However, due to the faintness of standard dense-gas tracers - HCN, HCO+, and HNC - dense gas in high-redshift galaxies remains largely unexplored. We present ALMA and NOEMA observations targeting HCN/HCO+/HNC (3-2) and (4-3) emission lines in eleven (mostly) gravitationally lensed dusty star-forming galaxies (DSFGs) at redshift z = 1.6--3.2. We detect at least one line in 10 out of 11 galaxies. Altogether, we detect 34 dense-gas transitions, more than quadrupling the number of extant high-redshift detections. Additionally, in two targets, we detect lower-abundance CO isotopologues 13^CO and C^18O, as well as CN emission. We derive excitation coefficients for HCN, HCO+ and HNC in DSFGs, finding them to be systematically higher than those in nearby luminous infrared galaxies. Assuming a canonical dense-mass conversion factor (alpha_HCN = 10), we find that DSFGs have shorter dense- gas depletion times (median 23 Myr) than nearby galaxies (~60 Myr), with a star-forming efficiency per free-fall time of 1-2%, a factor of a few higher than in local galaxies. We find a wide range of dense-gas fractions, with HCN/CO ratios ranging between 0.01 and 0.15. Finally, we put the first constraints on the redshift evolution of the cosmic dense-gas density, which increases by a factor of 7+/-4 between z = 0 and z = 2.5, consistent with the evolution of the cosmic molecular-gas density.

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