Probing the Early Growth of Black Holes through Low-ReDshift LRD Survey ((LRDs)²)

Speaker

Dr. Xiaojing Lin (Tsinghua University) 

Abstract

Little Red Dots (LRDs), identified by JWST at z > 4, have emerged as one of JWST’s most surprising discoveries, sparking ongoing debate about their physical nature. Their unusual properties challenge conventional frameworks for BH growth and AGN evolution. The discovery of low-redshift LRDs (z < 1) in large-area spectroscopic surveys opens a new avenue for studying this population. In this talk, I will present results from our low-redshift LRD survey, (LRDs)², highlighting how low-z LRDs provide an ideal laboratory for studying their physical properties. Low-z LRDs can be characterized in substantially greater detail, while growing samples from SDSS and DESI enable statistical studies of their demographics and physical properties. Together, these results will advance our understanding of the early growth of BHs and their connection to galaxy evolution across cosmic time.

Unveiling the Role of AGN in Post-Starburst Galaxies: Quenching Mechanisms at Cosmic Noon

Speaker

Dr. Pallavi Patil (National Radio Astronomy Observatory) 

Abstract

One of the key problems in astrophysics is understanding how and why galaxies switch off their star formation, building the “red sequence” we observe in the local Universe. Post-starburst galaxies (PSBs), where a galaxy has recently undergone a massive starburst, are sufficiently common at z~1-2 that they may contribute significantly to the growth of the red sequence at this critical epoch. The role of active galactic nuclei (AGN) feedback in shutting star-formation in PSBs and driving the evolution from star-forming to quiescence remains a key question in galaxy evolution. Here, we present a large sample of high-z PSBs (0.5<z<3) selected using a Principal component analysis of 11-band photometry available in the UKIDSS Ultra Deep Field (UDS). We leveraged multi-wavelength datasets available to test the incidence of AGN, mainly obscured AGNs. Cross-matching of deep 1.4 GHz VLA imaging showed that only 1% of PSBs host radiatively inefficient, jetted AGNs, suggesting a low prevalence of jet-driven quenching at cosmic noon. We also present MIR imaging to check the presence of obscured AGN and study the cold gas content via dust emission during the quenching episode. Overall, our findings reveal the strong influence of stellar mass on the characteristics of PSBs, with more massive PSBs likely to reside in overdense regions and host AGNs. Finally, we discuss the implications of our study in providing robust constraints on different quenching mechanisms during a crucial epoch of cosmic time.

Seminar Connection

Zoom Registration, you will receive connection details by email after registration: 

https://alaska.zoom.us/meeting/register/V1okit8uSk2ql97gegbdzg