Institute for Nuclear and Particle Astrophysics (INPA) at LBNL
The INPA Seminar weekly talks are on Fridays, starting at 12:00 pm, unless informed otherwise. The seminar talk starts with a brief presentation of the weekly scientific news. Typically, the talks conclude by 1:00 pm. The seminars are held in the Sessler Conference Room, located in Bldg. 50A- 5132.
The committee members are:
The seminar schedule for the Institute for Nuclear and Particle Astrophysics (INPA) is tentative and becomes final a few days before the Friday talk.
Please send all suggestions for future INPA talks and speakers to the INPA Committee.
To be added to the INPA News Mailing List, please contact Erica Hall.
Special INPA Speaker: Sindhu Satyavolu (IFAE) Institut de Fisica d’Altes Energies
December 4 @ 11:00 am - 12:00 pm
Date: December 4, 2024
Time: 11:00 am – 12:00 pm
Location: Sessler Conference Room – 50A-5132 [Hybrid and In-Person]
Speaker: Sindhu Satyavolu (IFAE) Institut de Fisica d’Altes Energies
Title: Quasar proximity zones in a partially ionized IGM
Abstract: Proximity zones of quasars with redshifts z > 5.5 are unique probes of the growth of supermassive black holes, and a nuisance in the direct measurements of the mean free path of the photons that reionize the universe. Interestingly, such proximity zones have been at the centre of two observational puzzles in recent times: 1) about 10% of the measured proximity zone sizes in the quasar Lyman-alpha spectra seem to be too short to explain their black hole masses, and 2) when corrected for the proximity zones, the mean free path of ionizing photons at z ~ 6 appears to be much shorter than theoretical predictions. In this talk, I will present a model of quasar proximity zones that takes into account the patchiness of the ionization and thermal state of the IGM during reionization. I will show that the patchiness of reionization can relieve the tension between the proximity zone sizes and black hole masses to some degree, but not fully. Further, I will show how quasar proximity zones in an inhomogeneously ionized IGM affects mean free path measurements from rest-frame 912 A spectra at z ~ 6. By forward modelling the proximity zones, I will examine the consistency between the direct and indirect redshift-6 mean free path measurements. Finally, I will show that the observed distribution of proximity zone sizes can be explained by a model in which quasars are variable on timescales of ~10^6 yr and have short duty cycles. This conclusion, when combined with the measurements of black hole masses of these quasars, directly leads to a prediction of significant obscuration in high-redshift quasars. I will argue that measurements of this obscuration fraction using JWST can then place constraints on the seed mass and formation redshifts of black holes.
Join Zoom Meeting
https://lbnl.zoom.us/j/95016696011?pwd=Tk1XOW1Xd3RYRnlsc2tEYmRWZlVVZz09
Meeting ID: 950 1669 6011
Passcode: 247722
INPA guests from campus can now come to the lab early on Fridays. The INPA Common Room (50-5026) is reserved for our guests from 10:00 a.m. to 12:00 noon and from 1 p.m. to 5 p.m. Note that the seminars are now held in 50A-5132 to accommodate a more significant number of attendees.
CPTea Series (also known as INPA Tea Series)
The Physics Division CPTea Series invites you to an In-Person Tea Series 1st Friday of every month at 3:30 pm INPA Conference Room 50-5026.
Everyone is welcome to attend the open forum. Tea and light refreshments will be served.
INPA Common Room (50-5026)
Fridays
3:30 pm
Access to the Lab
For a shuttle pass, please email Erica Hall. The pass is only valid for the day of the seminar.