Euclid: Early Release Observations -- The star-formation history of massive early-type galaxies in the Perseus cluster

TL;DR

This study reconstructs the SFHs of massive early-type galaxies in the Perseus cluster by combining Euclid ERO imaging with UV and optical data, leveraging CIGALE SED fitting and UV-upturn models to interpret UV emission from old stellar populations. Spatially resolved SED fitting for the six most massive ETGs reveals old ages, metal-rich centers, UV upturns with temperatures around $\langle T_{UV,rad} \rangle \sim 2.6\times 10^{4}$ K, and rapid SF timescales ($\tau \lesssim 1500$ Myr). Integrated analyses show that most ETGs formed a substantial fraction ($>\sim 30$–$100\%$) of their stellar mass by $z\approx5$, with the most massive local ETGs attaining masses comparable to JWST red quiescent galaxies at $z>4.6$, suggesting local massive ETGs may be descendants of early quiescent systems. These results support a two-phase formation scenario in dense environments and demonstrate the potential of Euclid-scale, multi-wavelength, high-resolution data to trace galaxy assembly histories across cosmic time.

Abstract

The Euclid Early Release Observations (ERO) programme targeted the Perseus galaxy cluster in its central region over 0.7deg$^2$. We combined the exceptional image quality and depth of the ERO-Perseus with FUV and NUV observations from GALEX and AstroSat/UVIT, as well as $ugrizHα$ data from MegaCam at the CFHT, to deliver FUV-to-NIR magnitudes of the 87 brightest galaxies within the Perseus cluster. We reconstructed the star-formation history (SFH) of 59 early-type galaxies (ETGs) within the sample, through the spectral energy distribution (SED) fitting code CIGALE and state-of-the-art stellar population (SP) models to reproduce the galactic UV emission from hot, old, low-mass stars (i.e. the UV upturn). In addition, for the six most massive ETGs in Perseus [stellar masses $\log_{10}(M_{\ast}/M_{\odot}) \geq 10.3$], we analysed their spatially resolved SP through a radial SED fitting. In agreement with our previous work on Virgo ETGs, we found that (i) the majority of ETGs needs the presence of an UV upturn to explain their FUV emission, with temperatures $\langle T_{\rm UV}\rangle$~33800 K; (ii) ETGs have grown their stellar masses quickly, with SF timescales $τ\lesssim 1500$ Myr. We found that all ETGs in the sample have formed more than about 30% of their stellar masses at z~5, up to ~100%. At z~5, the stellar masses of the most massive nearby ETGs, which have present-day stellar masses $\log_{10}(M_{\ast}/M_{\odot})\gtrsim 10.8$, are then found to be comparable to those of the red quiescent galaxies observed by JWST at similar redshifts (z>4.6). This study can be extended to ETGs in the 14000 deg$^2$ extragalactic sky that will soon be observed by Euclid, in combination with those from other major upcoming surveys (e.g. Rubin/LSST), and UV observations, to ultimately assess whether the nearby massive ETGs represent the progeny of the massive high-z JWST red quiescent galaxies.

Figures (13)

• Figure 1: ${\rm FUV-NUV}$ (left) and ${\rm FUV}-\IE$ (right) colours as a function of stellar mass for the Perseus galaxies studied in this work and for the Virgo galaxies from the GUViCS data voyer14boselli14. Filled green squares (diamonds) indicate Perseus ETGs (unclassified) sources from meusinger20. Filled blue diamonds are Perseus LTGs, while the open red circle represents the central galaxy of Perseus, namely NGC 1275. Purple open triangles indicate Virgo LTGs, while Virgo ETGs are represented by purple open stars. M87, the central of Virgo, is also highlighted with an open red square. Black dashed lines are the magnitude limit curves for each corresponding colour for the Perseus observations. Circular apertures are defined in the FUV band starting with a radius equal to the $R_{\rm eff}$ in by EROPerseusOverview. Apertures were adjusted when needed to fully encompass the FUV emission, and checked against the $\IE$ images to avoid contamination, as in voyer14. We refer to Sect. \ref{['subsec:integr']} for more details.
• Figure 2: ${\rm FUV-NUV}$ (left) and ${\rm FUV}-\IE$ (right) colours as a function of the semimajor axis in kpc. Empty symbols indicate the values of the central colours calculated when a mask is not applied. The dotted lines connect the central unmasked regions to the successive regions. See Sect. \ref{['subsec:rad_analys']} for more details. Perseus ETGs are indicated with solid lines, while Virgo ETGs from martocchia25 are represented by dashed lines and purple colours. The grey dash-dotted vertical line indicates the projected radius within which a disc of dust is observed in the $\IE$ images of NGC 1270, NGC 1277, NGC 1278 and NGC 1281, see Sect. \ref{['subsec:dust']}.
• Figure 3: Images of the ETGs in the radial sample in the $\IE$ band plotted with an asinh scale.
• Figure 4: Top panels: images zoomed in the inner regions of NGC 1277, NGC 1278, and NGC 1281, from left to right. Bottom panels: extinction maps in the $\IE$ filter, $A_{\IE}$, constructed from the top panels. North is up and east is to the left.
• Figure 5: SED fitting results of galaxy properties for the radial sample of Perseus ETGs. From the upper left to the lower right: mass-weighted age, stellar metallicity, temperature of the UV upturn, and SF timescale as a function of the SMA/$R_{\rm eff}$. Shaded areas represent 1$\sigma$ errors.