Group Pre-processing in J1611+4026: Minor Rejuvenation of a Massive ETG fueled by Interaction-driven Gas Transfer

Abstract

Interactions within galaxy groups are fundamental drivers of galactic evolution, and establishing a direct observational link between the dynamical processes of satellite galaxies and the rejuvenation of massive host galaxies remains challenging. We present a multi-wavelength work of J1611+4026, a unique triple system characterised by a massive early-type host galaxy, Component C and two gas-rich companions, Components A and B, which are currently undergoing a major merger in its near environment. Utilising deep optical imaging from DESI-LS and spectroscopic data from DESI and P200, we employ 2D morphological decomposition using \textsc{GALIGHT} alongside joint spectrophotometric synthesis modelling with \textsc{BAGPIPES} and \textsc{CIGALE} to deconstruct the structural properties and star formation histories of the member galaxies. Crucially, we identify an asymmetric tidal tail extending $\sim$15.15 kpc from Component A, confirming the ongoing interaction between the companions. Although Component C appears quiescent in both morphology and spectroscopy, we reveal a subtle robust signal of ``minor rejuvenation'', characterised by significant internal dust extinction of $E(B-V) \sim 0.53$ and a UV excess. The reconstructed star formation history indicates a recent ($\sim$100 Myr) starburst that contributes a negligible fraction to the total stellar mass ($f_{\rm burst} < 0.1$ per cent). We propose that this activity is fueled by the accretion of metal-enriched gas stripped from the interacting companions. These results strongly suggest group pre-processing, where interactions between satellite galaxies drive low-level star formation in the massive host through gas transfer, providing a quantitative benchmark for interaction-driven evolution in dense environments.

Figures (12)

• Figure 1: Pseudo-color image of the J1611+4026 system covering a $40\arcsec \times 40\arcsec$ field of view. The blue arrows highlight the tidal tail of J1611+4026A. The white circles indicate the apertures used for photometry.
• Figure 2: Upper panel: DBSP/P200 spectra of Component A and B (left), and their pseudo-colour cutout image with observation slit (orange) overlapping on it (right). The black overlapping region denotes the stitching of the blue and red spectral bands, while the crossed circles indicate telluric absorption. Lower panel: DESI-DR1 spectrum of Component C, with its pseudo-colour image shown on the right.
• Figure 3: 2D decomposition of J1611+4026 system and the surrounding galaxies for the DESI g-band images with GALIGHT. For each panel, from top to bottom, represents Component A, Component B, and Component C. From left to right, represents data, model, data minus model (residual), and their surface brightness profile. The defect in the Component C data panel is intrinsic to the DESI-LS observational data; this region was masked during the fitting process to prevent any bias in the derived structural parameters.
• Figure 4: Best-fit SEDs for Components A, B, and C modelled with CIGALE. The details of the observational data fitting are introduced in \ref{['Section2.4']}, and the results are shown in \ref{['tab3']}. The details about the input parameters are shown in \ref{['tab_SED']}.
• Figure 5: Physical properties and evolutionary status of the Component A, B, and C system. Panel (a): The position of the Components on the SFMS at $z \sim 0.14$ from Popesso2023. The dashed line and grey shaded region represent the median relation and $\pm 0.5$ dex scatter. The red upward arrow indicates the lower limit for Component B, while the square denotes the SFR derived from SED fitting for Component C. Panel (b): Relationship between stellar mass and metallicity. The trend line is from Lian2018. Panel (c): Rest-frame UVJ diagram. Rest-frame U, V, and J magnitudes are estimated from the best- fit broadband SED (see \ref{['Section2.4']}). The solid lines delineate the boundaries of the quiescent (top left) and star-forming (bottom) populations, as defined by Schreiber2015. Component C resides near the quiescent wedge, consistent with its red colours, while Components A and B occupy the star-forming region. Panel (d): The reconstructed SFH of Component C derived from BAGPIPESCarnall2018. The main plot shows the posterior distribution of the SFR over cosmic time, whilst the inset highlights the recent epoch, revealing potential signatures of rejuvenation or low-level activity.