New paper: The Multiwavelength Spectrum of NGC 3115

Last week, in collaboration with astrophysicists from USA and China, our group’s paper was accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS). The paper is about the properties of the spectral energy density (SED) of the nearby galaxy NGC 3115, that hosts a billion solar mass black hole in a low-luminosity  active galactic nucleus (LLAGN). Behind the spectrum of this galaxy there is a lot of information about the state of the gas flow around the supermassive black hole.

This work is a compilation of observational data of NGC 3115 nucleus followed by modeling of the spectrum considering the electromagnetic processes for the case of a radiatively inefficient accretion flow (RIAF), as the observation suggests. The main part of the work is the analysis of the radio emission that can be well-explained only considering the synchrotron emission from the RIAF, without the need of relativistic jet arising from the LLAGN,

The main result of the paper is a tight constraint on the density profile (ρ) of the accretion flow ρ(r) ∝ r -0.73 +0.01-0.02 which implies an important mass-loss via subrelativistic outflows (i.e. winds) in the RIAF. Our modeling suggests a nonthermal population of electrons in the flow too, similarly to SgrA*—the supermassive black hole in the center of our Galaxy—models.

The main plot of the paper. In the left the thermal SED. In the right is a zoom in radio region of spectrum: the red dash-dotted line is the thermal component of electron population and the blue dashed line is due to the nonthermal electron population, the black solid line is the resulting spectrum.


Speeding up black hole radiative transfer with GPUs

Today we’ve had the first meeting of the group with the goal of accelerating radiative transfer calculations around black holes with graphical processing units (GPUs). The idea is that by porting the code to exploit the massive parallelism of GPUs, we will see a dramatic speedup (hopefully ~10-100x). We have an enthusiastic group of students!

We decided to proceed with NVIDIA CUDA rather than OpenCL due to the better documentation and more astrophysical examples available in CUDA to guide us.

We will try to have a beta version of the GPU-accelerated code by December, and a release candidate on May 2018. The main challenges–as usual with GPGPU–is writing the appropriate kernels and GPU memory management in order to reduce host-device data transfers as much as possible.

Stay tuned for exciting news on astrophysical high-performance computing by our group!


XLI SAB 2017

During the week of September 4th to 8th, 2017, the XLI SAB (Brazilian Astronomical Society) meeting took place in São Paulo. It was a week  when astronomers from all corners of Brazil got together to discuss about astronomy and astrophysics.

The SAB was created in 1974 and every year the association promotes this meeting. The main objective of the reunion is to integrate Brazilian researchers and to plan the future of the astronomy in Brazil.

The XLI SAB was a great event, it was close to 300 participants presenting their current work. It is a very prolific environment for any astronomer or astrophysicist to discuss and learn with other researchers.

The members of the IAG Black Hole Group were present and exhibited their interesting works about black holes and high energy astrophysics. Gustavo Soares, Phd student, presented about “Spectral simulations of accreting black holes”, Raniere Menezes, Phd student, presented other poster with the title “Optical observations of blazar candidates and unknown gamma-ray sources” and Ivan Almeida, MSc student, presented his work about “The multiwavelength spectrum of NGC 3115: Hot accretion flow properties“.

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