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RDATE:20231105T010000
TZOFFSETFROM:-0600
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RDATE:20241103T010000
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BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Astronomy Colloquium
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Astronomy Department and McDonald Observatory Personnel present overview
s of their work
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20200901T153000
DTEND;TZID=America/Chicago:20200901T163000
RECURRENCE-ID;TZID=America/Chicago:20200901T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:J. Colin Hill, Columbia University
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Abstract
Our understanding of cosmolo
gy remains plagued by the persistent tension between early- and late-univer
se inferences of the Hubble constant, H0. Amongst recent develop
ments, new results from the Atacama Cosmology Telescope (ACT) have further
reinforced the early-universe picture from Planck and other probes, cl
early demonstrating that systematic errors are not responsible for the "low
" values of H0 derived from these observations. I will begin by revie
wing the recent ACT results and placing these within an updated context for
the H0 tension. I will then focus on a particular well-motivated the
oretical scenario aiming to resolve the tension, the "early dark energy" (E
DE) model. This scenario invokes a new component in the early univers
e that acts to decrease the physical size of the sound horizon imprinted in
the cosmic microwave background (CMB) and thereby increase the inferred H0
value. However, as I will discuss, EDE models that can successfully&
nbsp;fit the CMB and local H0 data run into trouble when confronted with hi
gh-precision large-scale structure (LSS) data. I will show that
the inclusion of LSS data from the Dark Energy Survey and other large photo
metric surveys weakens evidence for the existence of EDE, and that further
inclusion of data from the Baryon Oscillation Spectroscopic Survey further
tightens the bound. A joint analysis of cosmological data sets withou
t local H0 data (e.g., SH0ES) shows no evidence for EDE, and yields an H0 v
alue that is in significant tension with local H0 measurements. Thus,
the EDE scenario as currently formulated is unlikely to restore cosmologic
al concordance. I will conclude with a look ahead to forthcoming CMB
measurements from ACT with substantially higher precision, which could prov
ide important clues toward an H0 tension resolution.
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/div>
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20200908T153000
DTEND;TZID=America/Chicago:20200908T163000
RECURRENCE-ID;TZID=America/Chicago:20200908T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Feige Wang, University of Arizona
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Exploring Reionization-Era Quasars
Abstract
The most distant luminous quasars provid
e unique probes to the formation of the earliest supermassive black holes (
SMBHs), the assembly of massive galaxies and the reionization of intergalac
tic medium. In this talk, I will review the ongoing quasar surveys which yi
eld a sizable sample of quasars at redshift z~7 and several luminous quasar
s at redshift beyond 7.5, deep into the epoch of reionization. These quasar
surveys allow the first measurement of quasar luminosity function and the
characterization of quasar evolution in the reionization-era. In addition,
the existence of billion solar mass black holes at redshift beyond 7.5 post
s stringent constraints on the theory of black hole formation and growth in
the early Universe. I will also present our projects for investigating qua
sar host galaxies using high resolution ALMA observations and studying the
large-scale environment of the earliest SMBHs with deep wide field imaging.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20200915T153000
DTEND;TZID=America/Chicago:20200915T163000
RECURRENCE-ID;TZID=America/Chicago:20200915T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Anne Jaskot, Williams College
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Illuminating Reionization with the Low-Redshift Lyman Contin
uum Survey
Abstract
The
reionization of the intergalactic medium (IGM) at z > 6 is one of the ma
jor transformations in the universe’s history, but we do not yet fully unde
rstand how it occurred. The most likely explanation is that Lyman continuum
(LyC) radiation escaped into the IGM from early star-forming galaxies. How
ever, most lower-redshift star-forming galaxies show little to no sign of L
yC escape, and IGM absorption prevents us from directly measuring LyC durin
g the epoch of reionization itself. To address this issue, we have undertak
en the Low-Redshift Lyman Continuum Survey, the largest survey of LyC emiss
ion at low redshift to date. With HST UV observations of 66 galaxies, we ha
ve tripled the number of low-redshift LyC detections, enabling us to system
atically test proposed indirect diagnostics of LyC and establish the physic
al properties of LyC-emitting galaxies. I will share the initial results fr
om the survey and their implications for our understanding of cosmic reioni
zation.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20200922T153000
DTEND;TZID=America/Chicago:20200922T163000
RECURRENCE-ID;TZID=America/Chicago:20200922T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Thaisa Storchi-Bergmann, Federal University of Rio Grande do Sul (Brazil)
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Observational Signatures of Feeding and Feedback Processes o
f Active Galactic Nuclei
Abstra
ct
Supermassive black holes (SMBHs) grow at the centre of galaxies i
n consonance with them. In this talk, I will first discuss observational si
gnatures of the mass-feeding mechanisms that lead to this growth in active
galactic nuclei (AGNs), from extragalactic down to galactic and nuclear sca
les. Once triggered, the nuclear activity produces feedback in the form of
radiation, mass outflows and jets associated with the accretion flow to the
SMBH. I will then concentrate on results from resolved Integral Field Spec
troscopic (IFS) studies, including those of my research group AGNIFS. Most
observational signatures of feeding and feedback processes in such studies
are detected via the isolation of non-circular gas motions -- inflows and o
utflows that can be used to gauge the mass budget of the AGN feeding and th
e power and impact of gas outflows on the host galaxy. I will also discuss
the uncertainties that plague the determination of this impact, that includ
e uncertainties on the geometry and extent of the outflows as well as of th
e gas density in the outflows.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20200929T153000
DTEND;TZID=America/Chicago:20200929T163000
RECURRENCE-ID;TZID=America/Chicago:20200929T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Francis-Yan Cyr-Racine, University of New Mexico
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Cosmic Expansion, Neutrinos, and the Model that Refuses
to Die
Abstract
Local measure
ments of the Hubble parameter are increasingly in tension with the value in
ferred from a LCDM fit to the cosmic microwave background (CMB) and baryon
acoustic oscillation (BAO) data. Taken at face value, this tension might be
pointing towards physics beyond LCDM. We will briefly review how these dif
ferent measurements are done, highlighting which scales and epochs they are
probing. I’ll then argue that the most promising class of solutions to thi
s tension involves increasing the energy density of the Universe close to t
he epoch of matter-radiation equality. If you ask a particle physicist, the
y would tell you that the most natural way to do this is to have new relati
vistic particles at the epoch probed by the CMB.
We describe th
e appealing and problematic features of this proposed solution, showing tha
t it is in general challenging to resolve the tension between CMB, BAO, and
distance ladder measurements. We then ask: What about neutrinos? Could the
se pesky little particles have anything to do with our collective cosmologi
cal headache? In answering this question, we uncover potential new physics
in the neutrino sector that is so out-of-this-world that it should be sever
ely ruled out by the latest cosmological data. Or is it? I will discuss thi
s rather strange physical model that apparently refuses to die when confron
ted with new data, and what it might be telling us about the tensions we ar
e currently facing.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20201006T153000
DTEND;TZID=America/Chicago:20201006T163000
RECURRENCE-ID;TZID=America/Chicago:20201006T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Paula Jofré, Universidad Diego Portales (Chile)
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Stellar Phylogenies: Using tools from evolutionary biology t
o reconstruct the history of the Milky Way
Abstract
Galaxy evolution can be studied using the abund
ance ratios of long lived stars, which serve as fossil records of the chemi
cal composition from the gas clouds they formed. It is standard in our fiel
d to use the these fossil records to study how the chemical information is
inherited from one stellar generation to the next using the principle of de
scent with modification, and therefore underpin evolution. What is novel is
that this very principle allows us to further depict the patterns of desce
nt among stars as an evolutionary tree. Today, in all branches of biology,
evolutionary trees (more generally known as phylogenies) are a major tool f
or analysing the pattern and process of evolutionary history. In this talk,
I will show how we can adapt these tools and use it to study the history o
f the Milky Way.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20201013T153000
DTEND;TZID=America/Chicago:20201013T163000
RECURRENCE-ID;TZID=America/Chicago:20201013T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Marta L. Bryan, University of California, Berkeley
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Exploring the Formation and Evolution of Planetary Systems
em>
Abstract
Over the past tw
o decades thousands of planets with an extraordinary diversity of propertie
s have been discovered orbiting nearby stars. Many of these exoplanet
ary systems challenge our narrative for how planets form and evolve, motiva
ting the search for observational clues to the underlying mechanisms that l
ed to this diversity. In this talk I will describe my work using a wi
de range of observational techniques to uncover these underlying mechanisms
. I will constrain the physics of gas giant formation and evolution b
y discerning population statistics, system architectures, rotation rates, a
nd atmospheric compositions of gas giant planets. I will then discuss
the effect that outer gas giants have on the inner architectures of planet
ary systems by exploring differences in inner planet masses, separations, m
ultiplicities, and orbital properties. Finally, I will highlight the
key role that next generation instruments and telescopes such as the GMT wi
ll play by extending these novel observations to entirely new classes of pl
anets.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20201020T153000
DTEND;TZID=America/Chicago:20201020T163000
RECURRENCE-ID;TZID=America/Chicago:20201020T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Yuan-Sen Ting, Institute for Advanced Study
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Galactic Archaeology 2.0
Abstract
The ultimate goal of Galactic Archaeology is
to use stars as tracers to unravel the evolutionary history of our own gal
axy, The Milky Way. Galactic Archaeology today is a fundamentally different
field than it was just a decade ago. The order of magnitude of change has
been powered by our ability to gather extraordinarily large data sets from
ever more powerful instruments. With big data, Galactic archaeology has als
o taken a quantum leap forward in its relationship with statistics and mach
ine learning. In this talk, I will discuss how the characterization of the
chemical and kinematic properties of stars can unveil the subtle engines th
at drive the evolution of the Milky Way and whose exhaust leaves traces in
gentle variations that are now perceptible with statistics. I will also dem
onstrate how machine learning could alleviate many impasses that bottleneck
Galactic Archaeology. In particular, I will illustrate how to model Galact
ic dynamics with a non-parametric gravitational potential. I will also disc
uss a better-characterization of non-Gaussianity and auto-calibration of im
perfect synthetic simulations with large datasets via machine learning.
DTSTAMP:20240329T072143Z
DTSTART;TZID=America/Chicago:20201027T153000
DTEND;TZID=America/Chicago:20201027T163000
RECURRENCE-ID;TZID=America/Chicago:20201027T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:d42d8f518e8c93fe6752c3ad0557d318
CATEGORIES:Astronomy Colloquium
SUMMARY:Zoltan Haiman, Columbia University
LOCATION:Online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE: