New paper: Winds and feedback from supermassive black holes fed at low rates

We have a new paper out now on arXiv and submitted to the MNRAS: Winds and feedback from supermassive black holes accreting at low rates: Hydrodynamical treatment. This paper is the outcome of my MSc dissertation.


In this work we studied how accreting supermassive black holes generate winds that can potentially interact with the host galaxy. Our target was an active galactic nuclei (AGN) with very low accretion rates, like the famous M87*. Can these underfed systems generate powerful winds that will change the fate of the whole galaxy?

We performed diverse simulations of accretion disc flows around Schwarzschild black holes under an hydrodynamic treatment. Our simulations were some of the longest ones of our knowledge. The results show that some systems can create powerful thermally driven black hole winds that can be related to what we call “AGN feedback”. AGN feedback can be understood as the interaction between the ejected material/energy from the accretion flow and the host galaxy, this effect is crucial to understand galaxy evolution and currently it is a very active topic of research in astronomy. With this work we explored the possibility of thermally driven winds as a mechanism to explain this effect.

In the video below we show one of the simulations. On the top we have the gas density and each horizontal panel is the same disc but with different zoom levels, the scale is in Schwarzschild radius. On the bottom of the video we plot the wind efficiency. In practical terms, higher values here indicate stronger material ejection and production of more powerful winds.

For more details, please read our paper.

This work was supported in part by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) under grant 2017/01461-2 and grant 2016/24857-6.fapesp_logo-lowres

Astrophysicists Arts & Culture

Science and art are two fascinating human creations. They both have the power to represent the world in two completely different approaches. In our work, we chose the first one and we always try to coldly describe the physical properties of the cosmos.

But we are humans too, and art fans. In a casual group lunch we take some photos and using the Google Arts & Culture app we find the artistic counterparts for each of the present group members. The result you can see in the following image.

Black Hole Group members - Artistic Counterpart

We have some good matches and other funny ones, in the end we all agree that the app has a good machine learning code, but this is a topic for other post. After I have seen all these artistic work I just hope that the app is correct and that we are beautiful as these paintings.

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.


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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