Measuring the total infrared light from galaxy clusters at z = 0.5–1.6: connecting stellar populations to dusty star formation

Abstract

Massive galaxy clusters undergo strong evolution from z ∼ 1.6 to z ∼ 0.5, with overdense environments at high-z characterized by abundant dust-obscured star formation and stellar mass growth which rapidly give way to widespread quenching. Data spanning the near- to far- infrared (IR) can directly trace this transformation; however, such studies have largely been limited to the massive galaxy end of cluster populations. In this work, we present “total light” stacking techniques spanning 3.4 − 500 μm aimed at revealing the total cluster emission, including low-mass members and potential intracluster dust. We detail our procedures for WISE, Spitzer, and Herschel imaging, including corrections to recover the total stacked emission in the case of high fractions of detected galaxies. We apply our techniques to 232 well-studied log M200/M⊙ ∼ 13.8 clusters in multiple redshift bins, recovering extended cluster emission at all wavelengths. We measure the averaged IR radial profiles and spectral energy distributions (SEDs), quantifying the total stellar and dust content. The near-IR profiles are well described by an NFW model with a high (c ∼ 7) concentration. Dust emission is similarly concentrated, albeit suppressed at r ≲ 0.3 Mpc. The measured SEDs lack warm dust, consistent with the colder SEDs of low-mass galaxies. We derive total stellar masses consistent with the theoretical Mhalo − M⋆ relation and specific-star formation rates that evolve strongly with redshift, echoing that of log M⋆/M⊙ ≳ 10 cluster galaxies. Separating out the massive population reveals the majority of cluster far-IR emission ($\sim 70-80\%$) is provided by the low-mass constituents, which differs from field galaxies. This effect may be a combination of mass-dependent quenching and excess dust in low-mass cluster galaxies.

Measuring the Total Ultraviolet Light from Galaxy Clusters at z=0.5-1.6: The Balance of Obscured and Unobscured Star-Formation

“…The blue shaded region represents the 3σ domain of 10 10 < M * /M < 10 11 galaxies predicted from the total SFRIR. All of the unobscured SF we measure could be attributed to low mass galaxies, which is consistent with the high contribution of this population to SFRIR (Alberts et al 2021), and their relatively low obscured fractions.…”

“…As galaxies fall into the inner regions of clusters, they experience progressively more gas stripping in the outer disk regions, while simultaneously processing denser gas within the plane of the disk into stars. In particular, simulations show that most of a star-forming galaxy's halo gas is stripped before arriving at the virial radius of the host cluster, but that star-forming disks remain unperturbed until The shaded grey regions encapsulates the 3σ domain of predicted unobscured star-formation rates arising from 10 9 < M * /M < 10 10 galaxies assuming their fractional contribution to SFRIR of 70% (Alberts et al 2021), and that the obscured fraction of star-formation is field-like (Whitaker et al 2017). The blue shaded region represents the 3σ domain of 10 10 < M * /M < 10 11 galaxies predicted from the total SFRIR.…”

“…Optical and near-IR surveys can reach stellar mass limits of ∼ 10 9 M (van der Burg et al 2018); however, such sensitivity is not yet possible at UV and IR wavelengths where significant star-formation is detected in massive cluster galaxies (Haines et al 2011;Alberts et al 2016). To push the study of cluster members to higher redshifts while accounting for the light from less massive and faint galaxies that typically go undetected, Alberts et al 2021 (hereafter A21) developed a "total light" stacking method whereby nearthrough far-IR maps of many galaxy clusters were averaged to study the total cluster spectral energy distribution (SED) from z ∼ 0.5 − 1.6. They find the SED to be well-fit by a star-forming galaxy template, albeit with less warm dust than found in massive star-forming galaxies (Kirkpatrick et al 2015), and finding that the star-formation in the average cluster from z ∼ 0.5−1.6 is predominantly occurring within M * /M < 10 10 galaxies.…”

“…This paper is organized as follows: in Section 2 we describe the GALEX/N U V data. Section 3 summarizes our total light stacking method (Alberts et al 2021), and notable modifications for the treatment of GALEX data. Section 4 explores the results of combined UV through IR stacked cluster spectral energy distributions and radial profiles, which we discuss in further detail in Section 5.…”

Rapid build-up of the stellar content in the protocluster core SPT2349$-$56 at $z\,{=}\,4.3$

“…We see that the shapes of the stellar mass curves between the protoclusters and the 𝑧 1 clusters are similar, although the slope of the protoclusters becomes shallower than the slope of the 𝑧 = 1 clusters at large radii. It is interesting to note that a similar study (Alberts et al 2021) investigating stacks of galaxy clusters between 𝑧 = 0.5 and 1.6 in the near-infrared (3-8 𝜇m in the rest-frame) found similarly-concentrated light profiles, with NFW concentration parameters around 7; this near-infrared light is expected to trace stellar mass. They also investigated stacks in the far-infrared (250-500 𝜇m in the rest-frame), tracing dust emission and SFR, and found concentration parameters comparable to the near-infrared light.…”