Astrophysics Colloquium schedule
Wednesdays, 3:30-4:30 pm
The Astronomy Colloquia Meetings are held in the P&A building, room 1-434. Zoom information sent in email.
The UCLA Department of Physics & Astronomy Astrophysics group established the Astrophysics Colloquium speaking series 20+ year ago. Throughout the academic year, distinguished speakers travel to UCLA to share their latest research. The department sponsors and organizes these events to encourage collaboration within the field. This exposure is critical for our graduate students particular. The content shared in these events broaden their academic horizons. Additionally, the colloquium provide opportunities for our students to network with other specialists and peers.
Help us continue this enriching speaking series by making a donation online here. Gifts to the Astronomy and Colloquium Fund offset event costs including those related to speaker travel. Support from our event attendees and donors is greatly appreciated. For check instructions or other giving related questions, please contact Madeleine Martin at mmartin@support.ucla.edu or (310) 882-3633.
Fall 2024
October 2, 2024
Jason Rhodes (JPL Nasa)
Mapping the Dark Universe with Euclid
Abstract: After 2 decades of preparation, the European Space Agency’s Euclid space telescope was launched on July 1, 2023. Euclid’s primary goal is to study the dark universe and help us better understand the enigmatic dark matter and dark energy that make up the bulk of the universe. I will talk about my personal journey in bringing Euclid to fruition, give the details of the Euclid telescope and instruments that make it so powerful as a dark energy probe, and talk about the science (cosmology and other) that will be enabled by Euclid’s deep (50 square degrees) and wide (14,000 square degrees) sky surveys. I will also talk about the time scale for Euclid data to become available to the worldwide astronomical community.
October 9, 2024
Sofia Rojas Ruiz (UCLA)
The BoRG-JWST survey on Spectroscopically-confirmed UV-Bright Galaxies at z = 7 - 9 selected from Independent Sight Lines
Abstract: Quantifying the abundance and properties of bright galaxies in the early universe is essential to study galaxy formation and evolution since cosmic dawn. To study a statistically robust sample of galaxies against cosmic variance in the early universe, we selected bright galaxies in over 200 independent sight lines with HST imaging from the Brightest of Reionizing Galaxies Survey (BoRG). We then used JWST/NIRSpec PRISM observations to spectroscopically confirm the redshift of these bright (M_UV ≲ −20 mag) galaxies and characterize their properties from their rest-frame UV-to-optical spectral features. In this talk, I will introduce the key science questions we are addressing with this BoRG-JWST survey and will focus on the discoveries from studying the abundance and mass-to-light (M/L) ratio of z=7-9 galaxies in the survey. We are able to constrain, for the first time, the bright end of the rest-UV luminosity function (UVLF) at z~8 from spectroscopically-confirmed galaxies over eight independent fields. We find that the number density is higher than found using imaging over JWST legacy fields, suggesting the latter may be significantly affected by cosmic variance, and thus reducing the tension with recent findings from JWST at z > 10 and comparable to models invoking little dust attenuation and bursty star formation. We also use the spectra of these galaxies to infer their stellar masses and M/L ratios relative to other HST and JWST studies. We show that the stellar mass scales almost linearly with UV luminosity, albeit intrinsic scatter, consistent with stochastic bursts of star formation in early galaxy formation.
October 16, 2024
JWST deadline, no colloquium
October 23, 2024
Zoltan Haiman (Columbia University)
Gravitational wave and electromagnetic signatures of binary black holes with circumbinary gas
Abstract: Binary black holes (BHBs) embedded in dense gas hold the
promise of so-called "multi-messenger astrophysics": when they are
detected both through gravitational waves (GWs) and electromagnetic
(EM) observations, they will enable novel science. This is true both
for massive BHBs, whose GWs will be detectable by the future LISA
satellite and by on-going pulsar timing arrays (PTAs), as well as for
stellar-mass BHBs detected through ground-based GW detectors. In both
cases, identifying the coalescing binaries through their EM signatures
will help clarify their astrophysical origin and yield novel probes of
cosmology, fundamental physics, and accretion physics. In this talk,
I will describe how circumbinary gas may produce characteristic EM
signatures for both massive and stellar-mass BHBs, based on analytic
models as well as hydrodynamical simulations. I will also argue that
in both cases, some coalescing binaries may have already been detected
in optical surveys, providing clues about their origin.
October 30, 2024
Tod Lauer (Noirlab)
How Dark is Space?
Abstract: We used NASA’s New Horizons spacecraft to measure the cosmic optical background (COB) intensity integrated over 0.4 ≲ λ ≲ 0.9 μm. The survey comprises 16 high Galactic-latitude fields. Images were obtained with the LORRI camera when New Horizons was 57 AU distant from the Sun. As such, the sky intensity measurements were unaffected by zodiacal light, which strongly interferes with COB measurements attempted from the inner solar system. The survey yields a highly significant detection (6.8σ) of the COB at 11.16 ± 1.65 (1.47 sys, 0.75 ran) nW m‾² sr‾¹ at the LORRI pivot wavelength of 0.608 μm. The estimated integrated intensity from background galaxies, 8.17 ± 1.18 nW m‾² sr‾¹, can account for the great majority of this signal. The rest of the COB signal is formally classified as anomalous intensity but is not significantly different from zero. The simplest interpretation is that the COB is completely due to galaxies.
November 6, 2024
AstroBash - No colloq
November 13, 2024
Vicky Kaspi
The Mystery of Fast Radio Bursts
Fast Radio Bursts are a recently discovered phenomenon consisting of brief (typically few millisecond) bursts of radio waves coming from far outside our Milky Way galaxy, indeed from cosmological distances. Their origin is unknown. I will review what is known about these mysterious sources, and how they can act as novel probes of the matter distribution in the Universe. I will focus on results from the CHIME Fast Radio Burst Project, which uses a new Canadian digital radio telescope that is revolutionizing our view of the fast transient sky. I will also introduce the CHIME/FRB Outriggers, which will enable precise sky localizations for >1000 CHIME FRBs, hence permit host galaxy ID and redshift determinations.
November 20, 2024
No colloquium
November 27, 2024
Thanksgiving - No colloquium
December 4, 2024
Debra Fischer