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TZOFFSETFROM:-0600
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RDATE:20231105T010000
TZOFFSETFROM:-0600
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BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Astronomy Colloquium
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Title: TBA
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20190903T153000
DTEND;TZID=America/Chicago:20190903T163000
SEQUENCE:0
RRULE:FREQ=WEEKLY;UNTIL=20191204T000000Z;INTERVAL=1;BYDAY=TU
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Postdoc Colloquium
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Speakers:
Will Best, The University of Texas at Austin
Probing the Low-Mass End of the Initial Mass Function
Abstract
As the lowest-mass objects created by s
tar formation processes, brown dwarfs are essential to a complete understan
ding of star formation in our galaxy. The Initial Mass Function (IMF) for b
rown dwarfs remains poorly constrained due to incomplete samples of these f
aint objects in the Solar neighborhood and nearby star-forming regions. I w
ill describe two of my projects that take different approaches to probe the
low-mass IMF. One, we are using deep HST image maps of five benchmark Milk
y Way star-forming regions to comprehensively identify members down to plan
etary masses and explore variations of the IMF with star-forming environmen
t. Two, we have built a parallax-defined volume-limited sample of brown dwa
rfs within 25 pc of the Sun, and we are using population synthesis to const
rain the IMF and birth history that gave rise to the local brown dwarf popu
lation
Hope Chen
, The University of Texas at Austin
Core Evolution throug
h a Coherent Phase: An Updated Core Evolution Theory Told by Machine Learni
ng
Abstract
The conventional core
formation theory usually focuses on the gravitational boundedness of a cor
e. A core is assumed to form out of a gravitationally bound density s
tructure in a molecular cloud. In this talk, I will present the lates
t effort to examine the evolution of density structures found in a MHD simu
lation, in order to better understand the formation and evolution of star f
orming cores. By applying a principal component analysis (PCA) on the
density and velocity distributions, we find that there exists a prolonged
coherent phase in the evolution of density structures preceding the gravita
tional collapse and star formation in dense cores. We find that the c
oherent phase lasts ~ 3x10^5 to 4x10^5 years and is essential in the format
ion of star forming cores. By tracking the density structures in the
simulation and comparing them to structures identified in observations, we
characterize an evolutionary track in the parameter space and try to provid
e an updated theory of core formation and evolution.
<
/div>Chenxu Liu, The University of Tex
as at Austin
Searching for “Naked” Supermassive Black Hol
e Candidates with HETDEX
Abstract
As the largest blind spectroscopic survey ever undertaken, HETDEX offers t
he possibility to explore unique, rare and important objects in the univers
e. I will focus on discovery of (nearly) naked black holes. There is a supe
rmassive black hole (SMBH) in the nucleus of every galaxy, with their prope
rties often correlated with the bulges of their hosts. The hierarchical mer
ging of small galaxies thereby cause their black holes to merger. If a merg
er is tidally disrupted before the event is completed, one or both BHs coul
d recoil and remain without a galaxy (i.e., naked) for a few gigayears. The
se naked SMBHs will be optically faint, making them unlikely to be targeted
by almost all of the sky surveys. I will start from the introduction of th
e current status of the HETDEX survey, through our efforts to identify the
real lines, to the selection of the naked BH candidates with HDR1.
Yifan Zhou, The Uni
versity of Texas at Austin
Time-Resolved Observations of
Directly-imaged Planetary-Mass Companions and Exoplanets
Abstract
Condensate clouds pose a central challenge
in the atmospheric characterization of brown dwarfs and exoplanets. For va
riable brown dwarfs, it has been demonstrated that time-resolved observatio
ns place unique and strong constraints on their clouds. I will present my r
esearch on extending this technique to high-contrast observations of direct
ly-imaged planetary-mass companions and exoplanets. We have achieved sub-pe
rcent level precisions in high-contrast HST/WFC3/IR light curves. With such
precisions, we find the likelihood of detecting variability on planetary-m
ass companions is high. We also find tentative evidence for similar cloud s
tructures shared between planetary-mass companions and brown dwarfs. There
is substantial synergy between my studies and ongoing research at UT. I am
looking forward to exciting collaborations on these topics.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20190903T153000
DTEND;TZID=America/Chicago:20190903T163000
RECURRENCE-ID;TZID=America/Chicago:20190903T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Chat Hull, National Astronomical Observatory of Japan
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Magnetized star formation in the ALMA era
Abstract
New ALMA polarization observation
s continue to both expand and confound our understanding of the role played
by the magnetic field in low-mass star formation. The sample of very
young, Class 0 protostellar sources observed with high resolution and high
sensitivity with ALMA is now large enough that we are beginning to see the
same surprising features in many different sources. The first of the
se are magnetic field morphologies that beautifully trace the outflow cavit
y walls in several objects, indicating that the outflow has shaped the magn
etic field. The polarization along the cavities is strongly enhanced,
and in some cases is co-located with emission from UV-tracing molecules, s
uggesting that the origin of the enhanced polarization is the strong irradi
ation of the outflow cavities. The second, more puzzling set of featu
res are thin structures with well organized magnetic fields that are not as
sociated with outflow cavity walls, and yet have high polarization fraction
s in spite of being deeply embedded and far from any obvious source of the
photons necessary to align the grains. While on one hand these result
s challenge our understanding of both magnetic grain-alignment and grain gr
owth, they also have the potential to open up new windows into the dust-gra
in properties and radiation environments in young star-forming sources.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20190910T153000
DTEND;TZID=America/Chicago:20190910T163000
RECURRENCE-ID;TZID=America/Chicago:20190910T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Stephanie Douglas, Harvard-Smithsonian Center for Astrophysics
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Calibrating Stellar Activity, Rotation, and Multiplicity Wit
h Open Clusters
Abstract
Open clusters, such as the Pleiades, Praesepe, the Hyades, and NGC 6811, a
re critical benchmarks for calibrating stellar properties such as rotation
and magnetic activity. I will discuss recent rotation measurements in open
clusters, including the first periods measured for fully convective Hyads.
Discrepancies between open cluster data and models of angular momentum evol
ution imply that we still do not fully understand how magnetic fields affec
t stellar spin-down. I will show how we can use these clusters to test theo
ries of stellar magnetic fields. Finally, I will discuss the potential impa
ct of binary companions and protoplanetary disks on stellar angular momentu
m evolution.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20190917T153000
DTEND;TZID=America/Chicago:20190917T163000
RECURRENCE-ID;TZID=America/Chicago:20190917T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Rob Kennicutt, University of Arizona and Texas A&M University
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:The Schmidt Law at Sixty
Abstract
Sixty years have passed since Maarten Schmidt's co
njecture that star formation in galaxies was closely coupled to gas density
, and since that time the Schmidt law has become an indispensable tool for
interpreting, modeling, and simulating large-scale star formation in galaxi
es. Despite its success as a sub-grid "recipe" for the star formation
rate, however, we remain far away from an ab initio theory of sta
r formation, or even a clear understanding of the observed scaling laws the
mselves. This talk will review the current state of our observational
understanding of star formation in galaxies, and the complexity which lies
beneath the surface of the observed SFR scaling relations. We are wi
tnessing an observational and theoretical renaissance in the subject, as mu
lti-wavelength observations reveal the multi-scale nature of the star forma
tion process and the complex interactions which are taking place between co
smological, gravitational, interstellar, and stellar feedback processes on
these different scales. The picture which emerges is one in which the
superficially simple star formation scaling laws are manifestations of a h
ighly dynamic, complex, and self-regulating ecosystem in galactic disks.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20190924T153000
DTEND;TZID=America/Chicago:20190924T163000
RECURRENCE-ID;TZID=America/Chicago:20190924T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Charlie Conroy, Harvard-Smithsonian Center for Astrophysics
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Assembling our Galaxy
Abstract
I will review ongoing work aimed at understanding whe
n and how the major structural components of our Galaxy came into place. &n
bsp;The combination of Gaia and ground-based spectroscopic data has reveale
d that the stellar halo contains a remarkable degree of structure, and appe
ars to have formed partially by dynamical processes within the disk, and pa
rtially from accreted dwarf galaxies. Our simulations of the stellar
disk predict that the clustered nature of star formation imprints a high d
egree of structure in phase+chemistry space. This structure is now be
ing measured in the data, and promises to deliver new insights into the nat
ure of star formation and the dynamical history of the disk.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191001T153000
DTEND;TZID=America/Chicago:20191001T163000
RECURRENCE-ID;TZID=America/Chicago:20191001T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Jonathan Fortney, UC Santa Cruz
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Population-Level Planetary Physics
Abstract
Comparative planetary science,
as typically practiced over the past few decades, has looked for connectio
ns in physical processes between very small numbers of planets. Howev
er, due to the exoplanet revolution, and in particular for transiting plane
ts, we can use the astronomical perspective to look for trends in planetary
structure and physical processes that can only be seen with a large sample
size. This work complements the pursuit of more detailed science que
stions that can be asked in the solar system. I will discuss modeling
work that we have done to address several exoplanet topics, including the
"evaporation valley" for sub-Neptunes and super Earths, the giant planet ma
ss-metallicity relation, connections with atmospheric physics for these pla
nets, and the long-standing issue of the radius anomaly of hot Jupiters.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191008T153000
DTEND;TZID=America/Chicago:20191008T163000
RECURRENCE-ID;TZID=America/Chicago:20191008T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Heather Knutson, California Institute of Technology
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Exploring the Mysterious Origins of Super-Earths and Mini-Ne
ptunes
Abstract
<
p>Nearly a decade has passed since the discovery that planets with sizes in
termediate between that of the Earth and Neptune (“super-Earths” or “mini-N
eptunes”, depending on their densities) dominate the observed population of
close-in exoplanets. These planets have no solar system analogue, yet 30%
of Sun-like stars appear to have at least one (and often more) interior to
Mercury’s orbit. Did these planets form in situ, or did they migrate
inward from a more distant formation location? Either way, the implic
ations for our understanding of planet formation are bound to be significan
t. In my talk I will describe current efforts to address this questio
n by characterizing the bulk densities and compositions of these planets an
d searching for outer gas giant companions.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191015T153000
DTEND;TZID=America/Chicago:20191015T163000
RECURRENCE-ID;TZID=America/Chicago:20191015T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:BashFest 2019 - No colloquium
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
BashFest 2019 - No colloquium
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191022T153000
DTEND;TZID=America/Chicago:20191022T163000
RECURRENCE-ID;TZID=America/Chicago:20191022T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Michelle Ntampaka, Harvard-Smithsonian Center for Astrophysics
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
A Deep Learning Approach to Galaxy Cluster X-ray Masses
Abstract
I will pr
esent a machine-learning approach for estimating galaxy cluster masses from
Chandra x-ray mock observations. I will describe how a Convolut
ional Neural Network (CNN) -- a deep machine learning tool commonly us
ed in image recognition tasks -- can be used to infer cluster masses from t
hese images, reducing scatter in the mass estimates by up to 50%. I w
ill also show an interpretation tool, inspired by Google DeepDream, that ca
n be used to gain some physical insight into what the CNN sees.
div>
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191029T153000
DTEND;TZID=America/Chicago:20191029T163000
RECURRENCE-ID;TZID=America/Chicago:20191029T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Laura Sales, UC Riverside
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Dwarf Galaxies and their Dark Matter Content
p>
Abstract
Dwarf galaxies are e
xtremely diverse in their morphology, from rotationally-supported star-form
ing disks to gas-free spheroidal stellar systems with no star-formation and
negligible rotation. They are also believed to be the most dark matt
er dominated objects within the Lambda Cold Dark Matter (LCDM) model and, a
s such, they pose the most significant challenges to our cosmological scena
rio. LCDM galaxy formation models make two clear predictions: i) gala
xy formation should become increasingly inefficient in lower mass halos, im
plying that dwarfs are only able to collect a few percent of their baryonic
content, and (ii) dwarfs, like any galaxy, should be surrounded by a wealt
h of dark-matter substructure, implying that faint satellites of dwarfs sho
uld be common. I will present our current efforts using hydrodynamica
l simulations to address these predictions and to compare them with availab
le observational constraints including: stellar halos, the inventory of &nb
sp;dwarfs in the Local Volume and dwarf galaxies in dense cluster environme
nts such as Virgo and Coma.
Abstract
The reionization of
intergalactic hydrogen in the universe's first billion years was likely dr
iven by the first stars and galaxies. However, we will probably never obser
ve these 'first light' sources directly, but their properties can be inferr
ed through accurate measurements of the timeline and morphology of reioniza
tion. I will review the observational evidence for reionization and describ
e how we can use galaxies at our current observational frontiers to measure
the reionization process. In particular, Lyman alpha (Lyα) emission from g
alaxies can be used to probe the intergalactic medium at high redshifts, bu
t requires modelling physics from pc to Gpc scales. I will describe how we
can constrain reionization from spectroscopic observations of galaxies, foc
using on Lyα emission at z>6, by comparing observations to theoretical m
odels and simulations using statistical inference methods. I will present n
ew measurements which favour a late and relatively rapid reionization, and
place these in the context of high redshift galaxy formation. I will discus
s the challenges and prospects in understanding reionization and early gala
xy evolution with future facilities, such as JWST and upcoming 21cm experim
ents.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191112T153000
DTEND;TZID=America/Chicago:20191112T163000
RECURRENCE-ID;TZID=America/Chicago:20191112T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Lars Hernquist, Harvard-Smithsonian Center for Astrophysics
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
The IllustrisTNG Project
Abstract
A predictive theory of galaxy formation
remains elusive, even after more than 50 years of dedicated effort by
many renowned astrophysicists. The problem of galaxy formation is made
difficult by the large range in scales involved and the many non-line
ar physical processes at play. This talk describes a new generation of
numerical models that are designed to overcome these difficulties bas
ed on novel schemes for solving the fluid equations on a moving mesh.
In particular, I will describe an ongoing project that extends results
from the Illustris simulation by employing refined models for feedbac
k from stars and supermassive black holes. Several applications will&n
bsp;be described, including the color evolution of galaxies, low surface&nb
sp;brightness galaxies, and the statistics of large-scale structure, p
ertaining to high precision cosmological surveys.
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191119T153000
DTEND;TZID=America/Chicago:20191119T163000
RECURRENCE-ID;TZID=America/Chicago:20191119T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:No colloquium
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
No colloquium
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191126T153000
DTEND;TZID=America/Chicago:20191126T163000
RECURRENCE-ID;TZID=America/Chicago:20191126T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:68870e371b215553071f12072f523fb8
CATEGORIES:Astronomy Colloquium
SUMMARY:Eliot Quataert, UC Berkeley - cancelled
LOCATION:RLM 15.216B
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Colloquium cancelled
DTSTAMP:20240328T130357Z
DTSTART;TZID=America/Chicago:20191203T153000
DTEND;TZID=America/Chicago:20191203T163000
RECURRENCE-ID;TZID=America/Chicago:20191203T153000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
END:VCALENDAR