Session 1: Theoretical (astro)physics of compact objects
Chair: David Palmer (LANL/PennState)
09:05-09:25
Smoothed-Particle Hydrodynamics (SPH) has found immense success and adoption
in applications for the simulations of fluids, solids, and multi-phase flows
in both academia and industry. SPH formulations are based upon their Lagrangian,
particle, and mesh-free numerical methods when interpolating points of the
fluid, called particles, which move with the flow according to particle-particle
interactions and external forces. The advantages from these methods have led to
significant usage for simulating astrophysical systems. FleCSPH is a LANL-based
SPH code that utilizes the FleCSI framework for parallel data structures and
tree-based particle methods. FleCSPH calculates long-range forces via the Fast
Multipole Method (FMM). Additionally, FleCSPH makes use of astrophysical and
terrestrial material equations of state, external potentials, and a fixed
general-relativistic background metrics to model single astrophysical compact
objects. Since the beginning of FleCSPH development, it has been primarily used
for simulating computational astrophysics systems with a focus on compact star
mergers and their remnants.
The merging of cosmic, compact objects-neutron stars (NSs), black holes (BHs),
and white dwarfs (WDs) has been a growing field of interest, particularly after
the detection of the first gravitational wave (GW) signals associated with BH-BH
and NS-NS mergers. The properties of emissions observed from merger events vary
considerably due to the large diversity of compact binaries that end in mergers.
Understanding the properties of each merger group is the first step in exposing
the nature of many observed phenomena. We present the results of FleCSPH simulations
of the merging process of binary WDs, varying in resolution and comparing the
results to previous simulations. We pay close attention to the self-gravitating
disks which form in the simulations, surrounding the central compact object.
Though quarks are among the most fundamental particles in nature, we do not know
what states of matter they can form under all possible conditions. The problem of
predicting these states of matter and describing their properties at various
temperatures and densities, known as mapping the QCD phase diagram, has been a
major goal of theoretical and experimental research in recent years. The region of
low temperatures and intermediate densities is of particular interest to astrophysics
because these conditions are realized in the interiors of neutron stars. In this
presentation I will discuss a candidate state of matter that may arise in such
environments, known as the magnetic dual chiral density wave (MDCDW), which is
characterized by a spatially oscillating chiral condensate. Recent work has shown
that the presence of a magnetic field enhances the stability of this phase against
thermal fluctuations and extends the parameter space in which the condensate is
energetically favored. Future research on MDCDW may reveal insights and predictions
about the behavior of matter under these extreme conditions, paving the way for new
collaborations between nuclear physics and multi-messenger astronomy.
We investigate the hadron-quark phase transition at finite density in
the presence of a magnetic field taking into account the anisotropy
created by a uniform magnetic field in the system's equations of state.
We find a new anisotropic equilibrium condition that will drive the
first-order phase transition along the boundary between the two phases.
Fixing the magnetic field in the hadronic phase, the phase transition
is realized by increasing the baryonic chemical potential at zero
temperature. It is shown that the magnetic field is mildly boosted after
the system transitions from the hadronic to the quark phase. The
magnetic-field discontinuity between the two phases is supported by a
surface density of magnetic monopoles, which accumulate at the boundary
separating the two phases. Each phase is found to be paramagnetic with
higher magnetic susceptibility in the quark phase. The connection with
the physics of neutron stars will be highlighted throughout the talk.
Aric Hackebill (UTRGV)
10:05-10:25
In this presentation, it's reviewed the contribution to the heat capacity
of different quark matter phases that can appear inside a Neutron Star's
core, paying special attention to the magnetic dual chiral density wave
phase that is an energetically favored phase at intermediate densities and
low temperatures. In particular, we compare the results we obtain for the
different phases with the observational lower limit of the core heat capacity
established from observations of transiently accreting neutron stars. Our
results give insight regarding whether the possible dense phases that can be
realized are feasible to occur in the core of neutron stars or not.
Pedro Paulo Barboza Sanson (UTRGV)
10:25-10:50
Coffee Break
Session 2: Extreme frequencies
Chair: Brian Svoboda (NRAO)
10:50-11:10
Pulsars are rapidly rotating neutron stars with varied applications
in different areas of Physics. One of these included detecting
low-frequency gravitational waves via Pulsar Timing Arrays (PTAs)
by accurately timing a set of high precision pulsars. Constraining
the background noise due to other sources is essential for this effort.
One of the largest sources of error for PTAs is the time variable
effects of the interstellar medium and the Solar Wind. Since low-frequency
radio observations of pulsars are most sensitive to these variations,
they can test and improve the existing models used in PTAs and solar
wind studies. I will talk about the recent work we have been doing towards
testing the efficacy of these solar wind models and implications for PTAs,
using the long-term pulsar monitoring data of the Long Wavelength Array.
Pratik Kumar (UNM)
11:10-11:30
The upcoming release of the 12-year Fermi-LAT point source catalog
(4FGL-DR3) includes a variety of new unassociated gamma-ray sources,
adding to the already extensive list of high-energy astrophysical
objects which have no known counterpart in any other wavelength regime.
Here we present our ongoing efforts toward providing associations and
identifications for sources in this upcoming catalog. This includes
blind searches using multiple radio catalogs, as well as targeted searches
in particular fields of interest. We also highlight early results from
one such field: a parallax and proper motion for Cannonball Pulsar J0002+6216.
The Lunar Occultation Explorer (LOX) is an Astrophysics Explorer satellite
for proposal to NASA in collaboration with JHUAPL. This project demonstrates
the potential for LOX to map the galactic plane at MeV energies with
unprecedented angular resolution. Existing telescopes have only been able
to produce blurry images of the galaxy at MeV energies. Orbiting the moon,
LOX would generate higher resolution images by using the moon as an occulting
disk and gathering precise times for when sources rise and set. The lunar
coordinate location and altitude at each time step of the proposed orbit of
LOX are used to determine the location and angular size of the moon at each
time step from its perspective. The moon is then projected onto a simulated
MeV gamma ray sky that includes calculated diffuse emission and fake point
sources. Over a series of orbits, the localization of those sources are
simulated to demonstrate the mapping capabilities of LOX.
Madelyn Kinston (LANL)
11:50-12:15
Poster flash-talks
Chair: Brian Svoboda - cont.
Satellite mega constellations are an emerging concern in radio
frequency interference (RFI) mitigation. With tens of thousands of
satellites expected to launch over the next decade, it is important
to have tools to assess RFI from these satellites. This presentation
details a few possible models of all-sky satellite RFI estimation, as
well as early results from computational implementations.
Ian Birdwell (UNM)
As the field of gravitational wave detection grows, there is a need for
cheaper detection methods. Continuous gravitational waves are particularly
elusive, and there is not yet a working detection algorithm. We built a
deep neural network that can identify waves in generated noisy data. This
replicates, in a broadly accessible way, other recent models that have
attempted to identify CWs using machine learning. We found accuracies of 9
8% for low noise data, and for our highest noise group, we had accuracies
of just 49%. In future, we hope to further improve this algorithm by training
with more data.
Shira Goldhaber-Gordon (Institute for Computing in Research)
We explore how the assumption that ionization equilibrium modulates the modeled
intergalactic medium (IGM) at the end of the hydrogen Epoch of Reionization using
the cosmological radiation hydrodynamic Technicolor Dawn simulation. In neutral
and partially-ionized regions where the metagalactic ultraviolet background (UVB)
is weak, the ionization timescale exceeds the Hubble time. Assuming photoionization
equilibrium in such regions artificially boosts the ionization rate, accelerating
reionization. By contrast, the recombination time in photoionized regions, with
the result that assuming photoionization equilibrium artificially increases the
neutral hydrogen fraction. Using snapshots between 8 > z > 5, we compare the predicted
Lyman-alpha forest flux power spectrum with and without the assumption of ionization
equilibrium. Small scales (k > 0.1 rad s km^-1) exhibit reduced power from
7 < z < 5.5 in the photoionization equilibrium case while larger scales are
unaffected. This occurs for the same reasons: photoionization equilibrium artificially
suppresses the neutral fraction in self-shielded gas and boosts it in voids, suppressing
small-scale fluctuations in the ionization field. When the volume-averaged neutral
fraction drops below 10^-4, the signature of non-equilibrium ionizations on the LAF
disappears. Comparing with recent observations indicates that these non-equilibrium
effects are not yet observable in the LAF flux power spectrum.
Samir Kusmic (NMSU)
Over the past ~25 years, puzzling examples of radio-quiet, Type 1 quasars
with intrinsically weak or absent broad emission lines have been found.
The first systematic searches for these weak emission-line quasars (WLQs)
investigated the rest-frame equivalent width (EW) of the Lyalpha + N V
complex and revealed a high-redshift (z > 3) population, while identification
of lower-redshift (z < 3) WLQ candidates has relied on weak broad emission
lines at longer rest-frame wavelengths. We present spectroscopy covering
the Lyalpha + N V complex of six candidate low-redshift (0.9 < z < 1.5) WLQs
based on observations with the Hubble Space Telescope. These observations
allow us to explore unifying the low- and high-redshift WLQ populations via
EW[Lyalpha+NV], and the expanded wavelength coverage affords a better
understanding of the shapes of our targets' ionizing continua. Our results
are consistent with a physical model for rapid (i.e., near/super-Eddington)
accretion in which the innermost edges of a geometrically thick `slim disk'
shield a WLQ's broad emission line region from X-ray and extreme ultraviolet
radiation, effectively softening the incident ionizing continuum. Notably,
WLQs are observed to span a more extreme range of X-ray weakness than
`typical' quasars, yet there is no correlation found between their broad-line
emission weakness and X-ray weakness. We briefly discuss in-progress research
to extend the above results to lower-mass active galactic nuclei (M_BH ~ 1e6 M_sun)
through the combination of Chandra X-ray data with new observations from the
Very Large Array.
Jeremiah D. Paul (U.Nevada, Reno)
The central part of M31 is imaged in five FUV and NUV bands with AstroSat/UVIT.
The spatial structure of the bulge is analyzed in the highest sensitivity band
and shows a complex structure with prominent dust lanes. We combine the UVIT
data with archival SDSS, Spitzer and Hershel multi-band photometry, to carry
out SED fitting. The results of star formation and metallicity history of the
bulge are presented.
Denis Leahy (U.Calgary)
12:15-13:30
Lunch break
Session 3: Galaxies and the birth of stars
Chair: Juergen Ott (NRAO)
13:30-13:50
Recent wide-field integral field spectroscopy has revealed the detailed
properties of high redshift Lyman-alpha (Lya) nebulae, most often
targeted due to the presence of an active galactic nucleus (AGN). Here,
we use VLT/MUSE to resolve the morphology and kinematics of a nebula
initially identified due to strong Lya emission at z~3.2 (LABn06;
Nilsson et al. 2006). Our observations reveal a two-lobed Lya nebula,
at least ~173 pkpc in diameter, with a light-weighted centroid near a
mid-infrared source (within ~17.2 pkpc) that appears to host an obscured
AGN. The Lya emission near the AGN is also coincident in velocity with
the kinematic center of the nebula, suggesting that the nebula is both
morphologically and kinematically centered on the AGN. Compared to
AGN-selected Lya nebulae, the surface brightness profile of this nebula
follows a typical exponential profile at large radii (>25 pkpc), although
at small radii, the profile shows an unusual dip at the location of the
AGN. The kinematics and asymmetry are similar to, and the CIV and HeII
upper limits are consistent with other AGN-powered Lya nebulae. Double-peaked
and asymmetric line profiles suggest that Lya resonant scattering may be
important in this nebula. These results support the picture of the AGN
being responsible for powering a Lya nebula that is oriented roughly in
the plane of the sky. Further observations will explore whether the central
surface brightness depression is indicative of either an unusual gas or
dust distribution or variation in the ionizing output of the AGN over time.
Kelly N. Sanderson (NMSU)
13:50-14:10
"Green Bean" galaxies are rare, low redshift objects with extended
emission line nebulae. Nicknamed for their green colors in Sloan
Digital Sky Survey imaging, these galaxies are powered by active
galactic nuclei and have strong [OIII] lines in their spectra. Prior
work used selections in color-color space to find these objects.
While these selection criteria worked to find the initial sample of
"Green Beans," including 17 objects at a redshift of z~0.3, we wanted
to find more of these rare objects by selecting them based on their
physical properties rather than only their apparent colors. With our
"Green Chile" project, using simulated galaxies and their surrounding
nebulae, we have created new, physically motivated selection criteria
in color-color space based on continuum spectrum slope, [OIII] line
strength, and redshift. In this talk, we present a new sample of
"Green Bean" candidates. Future work will involve follow up observations
with Apache Point Observatory in order to confirm the nature of these
objects.
Audrey F. Dijeau (NMSU)
14:10-14:30
Even though high-mass stars (M > 8 Msun) shape the universe at all
scales, from their ionizing winds to their explosive deaths, how
they are formed is still one of the biggest unknowns in astronomy.
One proposed formation model is a scaled up version of the accretion
model that seems to work well for lower mass objects. Jets are key
ingredients in this formation scenario, since they dissipate excess
angular momentum and allow accretion to proceed. However, observing
massive young stellar objects (MYSOs) in their earliest protostellar
stages is to this day a challenge. Due to the large distances and short
time scales involved, the number of known ionized jets driven by MYSOs
is scarce, making the comparison of theoretical models with observations
a difficult task.
Using high resolution VLA cm observations, we have found a large set
of jet candidates driven by very early MYSOs. Most of these candidates
are unresolved and other probes are needed to confirm their jet nature.
SiO is a well-known molecular jet tracer, since its abundance is highly
enhanced in shocked gas regions due to the sputtering of dust grains.
To confirm the jet nature of the emission, we carried out VLA observations
toward a sample of 10 ionized jet candidates at 42 GHz looking for SiO
J=1-0 emission. In this talk we will present the preliminary results of
this work.
Tatiana M. Rodriguez (NMT)
14:30-14:50
Dense starless and gravitationally bound prestellar cores are uniquely suited
to provide a glimpse of the physical and chemical conditions prior to stellar
birth when initial conditions of star and planet formation are set. In recent
years, the detection of complex organic molecules (COMs), any molecule with at
least one carbon atom and six total atoms, in prestellar cores has sparked
interest in the star formation community due to astrochemical and astrobiological
implications. We've found that COMs are prevalent in the Taurus Molecular Cloud,
from our survey of 31 starless and prestellar cores, spanning a wide range of
evolutionary stages, where we detect methanol (CH3OH) in 100% of the cores
targeted and acetaldehyde (CH3CHO) in 68%. Additionally, in the dynamically and
chemically young starless core L1521E, also in Taurus, we've observed for the
first-time the higher complexity species dimethyl ether (CH3OCH3), methyl formate
(HCOOCH3) and vinyl cyanide (CH2CHCN), suggesting COMs are forming early and
often. In order to understand the mechanisms and conditions needed to form such
molecules in cold (10 K) and dense (10^5 cm^-3) prestellar core environments,
we need constraints on physical properties, such as central densities and radii.
To do this, we've focused on part of the L1495 Taurus region, B10, as it is young
and less evolved compared to other regions, with no protostars and thus no significant
feedback from surrounding star formation. The highest resolution (12'' and 19'')
dust continuum maps of B10 (at wavelengths of 1mm and 2mm), were taken with the
NIKA2 instrument on the IRAM 30meter radiotelescope in Pico Veleta, Spain. Grids
of 3D radiative transfer models for each of the prestellar cores embedded within
B10 have been run to find best-fit density, radii, opacity, and external radiation
field parameters. From these models we gain deeper physical understanding of prestellar
cores, including their evolutionary states, which in turn will tell us about the
conditions needed for COM chemistry to thrive.
Samantha Scibelli (U.Arizona)
14:50-15:00
Most radio astronomers have used some task or routine called "quack" to flag the
beginnings and ends of scans. However, I recently discovered that very few people
know where this procedure got its strange name. Interviews with several radio
astronomers and programmers revealed that nearly everyone made their own unique
assumptions to explain its origins. I eventually uncovered the truth, and it was
not what I expected.
Justin Linford (NRAO)
15:00-15:20
Coffee Break
Session 4: Instrumentation
Chair: Anna Kapinska (NRAO)
15:20-15:40
The Magdalena Ridge Observatory Interferometer (MROI) when completed will
be the most ambitious optical/infrared interferometer project built to date
-- having 10 telescopes on reconfigurable baselines of 28 stations and
instruments for fringe tracking and scientific discovery at infrared and
optical wavelengths. The Astrophysics 2020 Decadal survey panel report on
stellar studies indicated the crucial nature of OIR interferometry for answering
key questions about stellar physics and indicated that MROI should seek further
funding to complete the facility this decade. We are on our way to achieving
this goal under a new 5-year cooperative agreement with AFRL to complete three
telescopes and achieve first fringes and closure phase measurements in the next
few years. We will present an overview of our objectives, both in scientific
and space situational awareness regimes, as well as a schedule and plans for the
next several years.
Michelle J. Creech-Eakman (NMT/MROI)
15:40-16:00
The origin of the cosmic diffuse gamma-ray (CDG) background in the 0.3 - 10 MeV
energy range is a mystery that has persisted for over 40 years. The Mini
Astrophysical MeV Background Observatory (MAMBO) is a new CubeSat mission under
development at Los Alamos National Laboratory, motivated by the fact that, since
the MeV CDG is relatively bright, only a small detector is required to make
high-quality measurements of it. Indeed, the sensitivity of space-based gamma-ray
instruments to the CDG is limited not by size, but by the locally generated
instrumental background produced by interactions of energetic particles in
spacecraft materials. Comparatively tiny CubeSat platforms provide a uniquely
quiet environment relative to previous gamma-ray science missions. The MAMBO
mission will provide the best measurements ever made of the MeV CDG spectrum and
angular distribution, utilizing two key innovations: 1) low instrumental background
on a 12U CubeSat platform; and 2) an innovative shielded spectrometer design that
simultaneously measures signal and background. MAMBO will also partner with
commercial vendors for the CubeSat bus and ground station network in order to
reduce cost and development time. We describe the MAMBO instrument and mission
concept in detail, including simulations and laboratory measurements demonstrating
the key measurement concept.
The High Altitude Water Cherenkov (HAWC) Observatory, located in central Mexico
at 4100 m above sea level, is sensitive to gamma rays from 300 GeV to beyond
100 TeV and continuously observes a wide field-of-view (~2 sr). With its high
energy reach and large area coverage, HAWC is well-suited to perform unbiased
surveys of the TeV sky. This had lead to numerous studies: cataloging and
classifying TeV gamma-ray sources, setting limits on the Diffuse Gamma-Ray
Background and dark matter, and investigating galactic and extragalactic
extended sources as well as high-energy particle acceleration sites. This
presentation will be an overview of HAWC's latest findings on these subjects.
Mora Durocher (LANL)
16:20-16:40
The Long-Wavelength Array (LWA) radio telescope operates at two New Mexico
stations located in Socorro and Sevilleta with 256 antennas each. The science areas
include, but are not limited to: radio transients, pulsars, the era of reionization,
cosmic ray air showers, meteor radio afterglows, the Sun, Jovian decametric emission,
exoplanets, and the ionosphere. An expanded continent-wide LWA-Swarm would dramatically
enhance the broad range of astrophysics covered by the current LWA even further. The
first 64-antenna LWA-Swarm mini station is under construction at the VLA North Arm.
In addition to the science benefits, mini-stations also engage students in the
construction and operation of the instrument, taking the 13-antenna pathfinder at
Hillsdale College in Michigan as an example.
Timothy Dolch (UNM)
16:40-17:00
The next generation Very Large Array (ngVLA) is designed to accommodate
a wide variety of scientific observations in a frequency coverage of
~1.2 -- 116 GHz with up to 20 GHz of instantaneous sampled bandwidth.
Additionally, the ngVLA is designed to be a non-reconfigurable array,
aiming to deliver high sensitivity over ~4 orders of magnitude in
resolution. The configuration reference design (Rev. D) is composed of
three subsets distributed over a range of physical scales: a Main
Interferometric Array, a Short Baseline Array (SBA) and a Long Baseline
Array (LBA). Furthermore, the Main array is composed of 214 x 18 m
antennas distributed in three sub-components: a dense Core of diameter
4.3 km for high surface brightness sensitivity, a five-arm spiral
providing up to 39 km baselines called the Spiral subarray and a
Mid-baseline subarray with baselines up to ~1000 km. The SBA is
composed of 19 x 6 m closely packed antennas that provide information
on spacings shorter than 38 m, the minimum baselines that are possible
in the Core. Additionally, four of the 18 m antennas from the Main
subset will measure total power to fill in the shortest spacings not
well-sampled by the 6 m interferometer. The LBA has 30 x 18 m antenas
consisting of several outlying stations that contribute the
intercontinental-scale baselines (~9000 km) needed to achieve resolutions
of ~ 0.1 mas. The ngVLA is being designed to operate concurrently with
combinations of different subsets and/or subarrays to optimize the
performance depending on the scientific requirements. I will review some
of the techniques that we are using to characterize the subarrays and to
study their performance at both high and low resolution. Also, I will
present studies of the ngVLA imaging performance for specific use cases
demonstrating its capabilities for meeting the science requirements.
The making of new stars takes place inside molecular clouds, where dust obscuration limits the use of the classic techniques of optical astronomy. The study of stellar formation became feasible only when radio and infrared astronomies developed in the second half of the past century. In the 1950s, a new class of bright optical nebula was discovered: the Herbig-Haro (HH) objects. Mysteriously, these nebulae kept on shining without an embedded star to provide the energy. The presently accepted solution to the enigma is that the HH objects are regions shock-excited by jets from remote, embedded young stellar objects. The first observational results in the study of the formation of new stars revealed outflowing motions, in contrast to the expected infalling motions needed for a star to grow in mass from some sort of initial seed. After decades of research we now count with a paradigm that explains this and other paradoxes. Stars do form from the contraction of fragments of the molecular clouds and the process involves simultaneous outflow (traced by the jets) and infall (traced by the protoplanetary disks) motions. We are getting close to a deep understanding of our origins through the study of stellar and planetary formation in space.
Prof. Luis F. Rodriguez (UNAM)
Instructions for Presenters
Talks will be scheduled for 17 minutes, followed by 3
minutes for questions from the audience.
Posters will be posted online in the Poster Gallery
section of the symposium website a day before the event.
Poster presenters will have scheduled 5 minute 'flash-talks'
to introduce and advertise their posters during the symposium.
It is assumed that the poster presenters will prepare a poster
PDF and present a flash-talk on that poster. However, presenters
can also choose to only present the poster in the PDF form (online),
or to only present the flash-talk (live). Please, inform the
organiser if you would like to have such a request accommodated.
There is no strict flash-talk format, but please ensure it is not
longer than the allocated time (5 minutes).
Breakout rooms will be open throughout the day of the symposium
to facilitate informal science discussions that arise from the
talks and poster presentations. Additional breakout rooms will
be made available upon request for in-depth discussions.