[论文解读] MAGAZ3NE: Dust Deficiency in Ultramassive Quiescent Galaxies at $3

Wenjun Chang, Gillian Wilson+15 more|arXiv (Cornell University)|Jan 30, 2026

Galaxies: Formation, Evolution, Phenomena被引用 0

一句话总结

本研究使用 MAGAZ3NE 的五个光谱确认的超质量星系在 z>3 的 ALMA Band 7 观测；只有一个显示微弱的尘连续辐射，其余对象在极低尘埃含量的 ISM 中被约束为真正的静止星形成。

ABSTRACT

A major challenge in identifying massive quiescent galaxies at $z>3$ is distinguishing truly passive systems from dust-obscured star-forming galaxies, as both populations exhibit similar red ultraviolet (UV)-to-near-infrared (NIR) colors. In this work, we present ALMA Band 7 dust-continuum observations of five ultramassive galaxies (UMGs; $\log (M_\star / M_\odot) > 11$) spectroscopically confirmed at $z_{ m spec} > 3$ from the MAGAZ3NE survey. Our results reveal that only one galaxy shows a faint 870 \um\ dust continuum detection, while the remaining four UMGs are undetected down to the $3σ$ depth . By incorporating ALMA constraints into the spectral energy distribution analysis, we confirm that these UV-NIR-selected systems are truly quiescent UMGs, lying more than one dex below the star-forming main sequence with $\mathrm{\log (sSFR/Gyr^{-1}) < -1}$, thereby ruling out the possibility of obscured star formation. We then estimate dust masses using both spectral energy distribution modeling and modified blackbody fitting, with consistent results between the two methods. We find that three UMGs have evolved into extremely dust-poor quiescent galaxies, with $M_{\mathrm{dust}}/M_\star \lesssim 10^{-4}$, while the ALMA-detected galaxy has a comparatively higher dust reservoir with $M_{\mathrm{dust}}/M_\star \sim 10^{-3}$. Our results present the most massive and extremely dust-poor spectroscopically confirmed quiescent galaxies known at $3 < z < 4$, providing valuable observational constraints on rapid dust removal and quenching processes in the early universe. Future molecular line observations will be essential to directly measure the gas content and verify the efficiency of the depletion process.

研究动机与目标

• Motivate the identification of truly quiescent, ultramassive galaxies at z>3 and distinguish them from dust-obscured star-forming systems.
• Leverage high-resolution ALMA dust continuum data to break degeneracies in UV-to-NIR selection of quiescent galaxies.
• Quantify dust content and assess residual star formation and quenching pathways in the early universe.
• Compare dust mass estimates from SED modeling and single-band modified blackbody fits to test robustness.

提出的方法

• Acquire ALMA Band 7 (872 μm) continuum data for five MAGAZ3NE UMGs at zspec>3.
• Perform 2D Gaussian fitting to measure fluxes and stacking to assess non-detections.
• Fit UV-to-radio SEDs with CIGALE including AGN and radio components to derive stellar, SFR, and dust properties.
• Estimate dust masses from CIGALE Draine et al. (2014) templates and from single-temperature modified blackbody fits.
• Compare M_dust/M_* across galaxies and with literature MQGs to interpret dust evolution and quenching.
• Discuss AGN contributions using CIGALE parameters and radio data to separate star-formation and AGN heating.

Figure 1: From left to right: ALMA Band 7 (870 $\mu$ m) primary-beam-corrected continuum image of XMM-VID3-2457; the two-dimensional Gaussian model; the residual map after subtraction of the model, shown in units of the RMS; and the stacked continuum image of four non-detected galaxies. The 0.28″ $\

实验结果

研究问题

• RQ1 Are UV–NIR selected z>3 ultramassive galaxies truly quiescent, or dust-obscured star-forming systems?
• RQ2 What are the dust contents and dust-to-stellar mass fractions in these ultramassive quiescent galaxies at 3<z<4?
• RQ3 How consistent are dust masses derived from SED modeling versus single-band MBB fits?
• RQ4 What is the role of AGN activity in shaping the observed SEDs and dust emission of these systems?

主要发现

• Only one of the five UMGs is detected in ALMA Band 7 with 294 ± 33 μJy; the others are undetected at 3σ.
• All five objects lie more than 1 dex below the star-forming main sequence, consistent with quiescence at z>3.
• Dust masses from SED fitting and MBB fits are broadly consistent; M_dust/M_* ≲ 10^-4 for three UMGs and M_dust/M_* ∼ 10^-3 for the ALMA-detected galaxy.
• The ALMA-detected galaxy has the highest dust reservoir, while the others are extremely dust-poor, providing constraints on rapid dust removal and quenching.
• Two COSMOS UMGs show substantial AGN contributions and radio emission, affecting SED interpretation and requiring AGN components in fits.
• The results place the most massive and extremely dust-poor spectroscopically confirmed quiescent galaxies at 3<z<4, informing quenching processes in the early universe.

Figure 2: Rest-frame (RF) UVJ color-color diagram for 16 spectroscopically-confirmed UMG candidates (open cyan circles) presented in Forrest et al. ( 2020b ) and 12 spectroscopically-confirmed S-UMGs candidates (open orange circles) presented in Forrest et al. ( 2024 ) . The five UMGs from Forrest e