12 research outputs found
Machine Learning for Observational Cosmology
An array of large observational programs using ground-based and space-borne
telescopes is planned in the next decade. The forthcoming wide-field sky
surveys are expected to deliver a sheer volume of data exceeding an exabyte.
Processing the large amount of multiplex astronomical data is technically
challenging, and fully automated technologies based on machine learning and
artificial intelligence are urgently needed. Maximizing scientific returns from
the big data requires community-wide efforts. We summarize recent progress in
machine learning applications in observational cosmology. We also address
crucial issues in high-performance computing that are needed for the data
processing and statistical analysis.Comment: 55 pages, 8 figures, submitted to Reports on Progress in Physic
3D-Spatiotemporal Forecasting the Expansion of Supernova Shells Using Deep Learning toward High-Resolution Galaxy Simulations
Supernova (SN) plays an important role in galaxy formation and evolution. In
high-resolution galaxy simulations using massively parallel computing, short
integration timesteps for SNe are serious bottlenecks. This is an urgent issue
that needs to be resolved for future higher-resolution galaxy simulations. One
possible solution would be to use the Hamiltonian splitting method, in which
regions requiring short timesteps are integrated separately from the entire
system. To apply this method to the particles affected by SNe in a
smoothed-particle hydrodynamics simulation, we need to detect the shape of the
shell on and within which such SN-affected particles reside during the
subsequent global step in advance. In this paper, we develop a deep learning
model, 3D-MIM, to predict a shell expansion after a SN explosion. Trained on
turbulent cloud simulations with particle mass M, the
model accurately reproduces the anisotropic shell shape, where densities
decrease by over 10 per cent by the explosion. We also demonstrate that the
model properly predicts the shell radius in the uniform medium beyond the
training dataset of inhomogeneous turbulent clouds. We conclude that our model
enables the forecast of the shell and its interior where SN-affected particles
will be present.Comment: 14 pages, 14 figures, 3 tables, accepted for MNRA
Surrogate Modeling for Computationally Expensive Simulations of Supernovae in High-Resolution Galaxy Simulations
Some stars are known to explode at the end of their lives, called supernovae
(SNe). The substantial amount of matter and energy that SNe release provides
significant feedback to star formation and gas dynamics in a galaxy. SNe
release a substantial amount of matter and energy to the interstellar medium,
resulting in significant feedback to star formation and gas dynamics in a
galaxy. While such feedback has a crucial role in galaxy formation and
evolution, in simulations of galaxy formation, it has only been implemented
using simple {\it sub-grid models} instead of numerically solving the evolution
of gas elements around SNe in detail due to a lack of resolution. We develop a
method combining machine learning and Gibbs sampling to predict how a supernova
(SN) affects the surrounding gas. The fidelity of our model in the thermal
energy and momentum distribution outperforms the low-resolution SN simulations.
Our method can replace the SN sub-grid models and help properly simulate
un-resolved SN feedback in galaxy formation simulations. We find that employing
our new approach reduces the necessary computational cost to 1 percent
compared to directly resolving SN feedback.Comment: 11 pages, 9 figures, Accepted for the NeurIPS 2023 AI4Science
Worksho
Large Population of ALMA Galaxies at z>6 with Very High [OIII]88um to [CII]158um Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit?
We present our new ALMA observations targeting [OIII]88um, [CII]158um,
[NII]122um, and dust continuum emission for three Lyman break galaxies at
z=6.0293-6.2037 identified in the Subaru/Hyper Suprime-Cam survey. We clearly
detect [OIII] and [CII] lines from all of the galaxies at 4.3-11.8sigma levels,
and identify multi-band dust continuum emission in two of the three galaxies,
allowing us to estimate infrared luminosities and dust temperatures
simultaneously. In conjunction with previous ALMA observations for six galaxies
at z>6, we confirm that all the nine z=6-9 galaxies have high [OIII]/[CII]
ratios of L[OIII]/L[CII]~3-20, ~10 times higher than z~0 galaxies. We also find
a positive correlation between the [OIII]/[CII] ratio and the Lya equivalent
width (EW) at the ~90% confidence level. We carefully investigate physical
origins of the high [OIII]/[CII] ratios at z=6-9 using Cloudy, and find that
high density of the interstellar medium, low C/O abundance ratio, and the
cosmic microwave background attenuation are responsible to only a part of the
z=6-9 galaxies. Instead, the observed high [OIII]/[CII] ratios are explained by
10-100 times higher ionization parameters or low photodissociation region (PDR)
covering fractions of 0-10%, both of which are consistent with our [NII]
observations. The latter scenario can be reproduced with a density bounded
nebula with PDR deficit, which would enhance the Lya, Lyman continuum, and C+
ionizing photons escape from galaxies, consistent with the [OIII]/[CII]-Lya EW
correlation we find.Comment: 20 pages, 18 figures, Accepted for publication in Ap
Large format imaging spectrograph for the Large Submillimeter Telescope (LST)
We present a conceptual study of a large format imaging spectrograph for next-generation large (50-m class) single-dish telescopes, i.e., the Large Submillimeter Telescope (LST) and Atacama Large Aperture Submillimeter Telescope (AtLAST). Recent discoveries of high-redshift star-forming galaxies at z=8-9 and candidate quiescent galaxies at z~6 indicate the onset of earliest star formation just a few 100 million years after the Big Bang (i.e., z = 12 - 15), and LST/AtLAST will provide a unique pathway to uncover spectroscopically-identified ``first forming galaxies’’ in the pre-reionization era, once it will be equipped with a large format imaging spectrograph. We describe the preliminary of 3-band, medium resolution (R=2000) imaging spectrograph with ~1.5 M detectors in total based on the KATANA concept (Karatsu et al.~2019), which exploits technologies of the integrated superconducting spectrometer (ISS) and a large-format imaging array like A-MKID.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Tera-Hertz Sensin
Erratum: “Possible Systematic Rotation in the Mature Stellar Population of a z = 9.1 Galaxy” ( 2022, ApJL, 933, L19 )
We present new observations with the Atacama Large Millimeter/submillimeter Array for a gravitationally lensed galaxy at z = 9.1, MACS1149-JD1. [O iii] 88 μm emission is detected at 10σ with a spatial resolution of ∼0.3 kpc in the source plane, enabling the most distant morphokinematic study of a galaxy. The [O iii] emission is distributed smoothly without any resolved clumps and shows a clear velocity gradient with ΔVobs/2σtot = 0.84 ± 0.23, where ΔVobs is the observed maximum velocity difference and σtot is the velocity dispersion measured in the spatially integrated line profile, suggesting a rotating system. Assuming a geometrically thin self-gravitating rotation disk model, we obtain , where Vrot and σV are the rotation velocity and velocity dispersion, respectively, still consistent with rotation. The resulting disk mass of M⊙ is consistent with being associated with the stellar mass identified with a 300 Myr old stellar population independently indicated by a Balmer break in the spectral energy distribution. We conclude that the most of the dynamical mass is associated with the previously identified mature stellar population that formed at z ∼ 15