The Interstellar Medium of Quiescent Galaxies and its Evolution With Time

Abstract

We characterise the basic far-IR properties and the gas mass fraction of massive ( log(M * /M ) ≈ 11.0) quiescent galaxies (QGs) and explore how these evolve from z = 2.0 to the present day. We use robust, multi-wavelength (mid-to far-IR and sub-millimetre to radio) stacking ensembles of homogeneously selected and mass complete samples of log(M * /M ) 10.8 QGs. We find that the dust to stellar mass ratio (M dust /M * ) rises steeply as a function of redshift up to z ∼ 1.0 and then remains flat at least out to z = 2.0. Using M dust as a proxy of gas mass (M gas ), we find a similar trend for the evolution of the gas mass fraction ( f gas ), with z > 1.0 QGs having f gas ≈ 7.0% (for solar metallicity). This f gas is three to ten times lower than that of normal star-forming galaxies (SFGs) at their corresponding redshift but 3 and 10 times larger compared to that of z = 0.5 and local QGs. Furthermore, the inferred gas depletion time scales are comparable to those of local SFGs and systematically longer than those of main sequence galaxies at their corresponding redshifts. Our analysis also reveals that the average dust temperature (T d ) of massive QGs remains roughly constant ( T d = 21.0 ± 2.0 K) at least out to z ≈ 2.0 and is substantially colder (∆T d ≈ 10 K) compared to that of SFGs. This motivated us to construct and release a redshift-invariant template IR SED, that we used to make predictions for ALMA observations and to explore systematic effects in the M gas estimates of massive, high−z QGs. Finally, we discuss how a simple model that considers progenitor bias can effectively reproduce the observed evolution of M dust /M * and f gas . Our results indicate universal initial interstellar medium conditions for quenched galaxies and a large degree of uniformity in their internal processes across cosmic time.

Revisiting the Color–Color Selection: Submillimeter and AGN Properties of NUV–r–J Selected Quiescent Galaxies

“…Our stacked 450 µm fluxes are also lower compared with results in Magdis et al (2021). They selected QG candidates with several color-color diagrams and stacked samples without 24 µm detection, so we compare our stacked fluxes of IR-radio-faint QGs with their results.…”

“…The fractions range from 7% to 12% in different redshift bins and do not have a strong redshift dependence. We conclude that the contamination of dusty SFGs is of ∼ 10% among the colorselected QG candidates, and that the contamination can The red triangles represent QGs in Magdis et al (2021). IR-radio-bright QGs in our work are defined as QG candidates either with 24 µm counterparts or with 3 GHz counterparts labeled with SFG flags in the VLA catalog (Smolčić et al 2017b), while IR-bright QGs in Man et al (2016) are defined as QG candidates with SFR derived from 24 µm over 100 M year −1 .…”

“…A possible explanation for the differences between the SCUBA-2 450 µm and Herschel 500 µm stacked fluxes is that the stacked Herschel fluxes were biased by source clustering at the scale of the large 35 Herschel 500 µm beam (e.g., Viero et al 2013, also see discussion in Béthermin et al 2017). Although Magdis et al (2021) modeled the emission of all the stacked images to separate surrounding sources, it appears that their 500 µm stacked fluxes are higher. Although Man et al (2016) applied SIMSTACK to stack and deblend simultaneously, it remains possible that the effects of source blending and clustering were not completely removed.…”

“…IR-radio-bright QGs in our work are defined as QG candidates either with 24 µm counterparts or with 3 GHz counterparts labeled with SFG flags in the VLA catalog (Smolčić et al 2017b), while IR-bright QGs in Man et al (2016) are defined as QG candidates with SFR derived from 24 µm over 100 M year −1 . QGs in Magdis et al (2021) are defined as QG candidates without 24 µm detection. The filled triangles are derived by the same LIR-SFR conversion with the other two works, while the open triangles are derived by the conversion described in their work.…”

“…Some studies measured the SFR by either applying SED fittings from the UV to mid-infrared bands (Fumagalli et al 2014;Merlin et al 2018;Carnall et al 2019;Toba et al 2019), using spectroscopic data (Schreiber et al 2018c;Belli et al 2017a), or measuring Hα emission (Belli et al 2017b). Others searched for far-infrared dust emissions using Spitzer observations (Fumagalli et al 2014;Man et al 2016;Gobat et al 2018;Magdis et al 2021), Herschel observations (Viero et al 2013;Man et al 2016;Straatman et al 2014;Merlin et al 2018;Gobat et al 2018;Magdis et al 2021) or Atacama Large Millimeter/submillimeter Array (ALMA) observations (Santini et al 2019;Schreiber et al 2018c;Simpson et al 2017). Others also searched for gas content in QG candidates (Sargent et al 2015;Young et al 2011).…”