3D Astrophysics Newsletter: 1.1

This is the first individual edition of the 3DA Newsletter. Individual submissions are send promptly as blog entries. Every two months a complete newsletter will be published with all submissions to this edition.


 

Redshift evolution of the space density of AGN with Lx > 1e43.2 erg/s, for various column densities

Redshift evolution of the space density of AGN with Lx > 1e43.2 erg/s, for various column densities

Obscuration-dependent evolution of Active Galactic Nuclei

J. Buchner, A. Georgakakis, K. Nandra, M. Brightman,
Ma.-L. Menzel, Z. Liu, Li-T. Hsu,
M. Salvato, C. Rangel, J. Aird,
A. Merloni, N. Ross

This work presents a Bayesian non-parametric method to reconstruct a smooth field. It is applied to reconstruct the space density of AGN as a function of X-ray luminosity, redshift and obscuring column density, all of which contribute severe selection biases. This method can be applied to a wide variety of 3D data sets (e.g. IFU spectral line fitting) to reconstruct the behaviour of a quantity and its uncertainty while only assuming smoothness across the field.

URL of preprint: http://arxiv.org/abs/1501.02805
Comments: The Astrophysical Journal, in press
Submitted by: Johannes Buchner

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3D Astrophysics Newsletter

Newsletter IllustrationAs part of this blog, we are starting a 3D Astrophysics Newsletter similar to other specialized newsletters in astronomy (see the new link on the menu bar at the top of the this page).
Newsletter are an effective way to publicize scientific work in the scientific community. I skim through the abstracts of most items in the newsletters that I subscribed to. They also generate a feel of community.
Our work is mainly related to the essentially 3D-character of astrophysical objects and we and others could benefit a lot from easily finding literature that is somehow related to 3D astrophysics. A newsletter might just be the right way to a better exchange of the experience around that is quickly increasing. Hopefully, with the 3D Astrophysics Newsletter we can contribute to an improved cross-talk between astronomers who are interested in all things 3D in astrophysics, be it the reconstruction of actual objects from observations, simulations, visualizations, rendering, software development, mathematical methods, etc. In order to give this newsletter a bit of a different look to other newsletter, we would like to include an eye-catching image with each entry and encourage contributors to include a comment to their submission choosing a figure from their publication that they would prefer to use for that purpose.

If you are interested in 3D Astrophysics and/or the newsletter, please subscribe to this blog and submit your paper abstracts to the simple Submission Form that can be accessed through the drop-down list when moving your cursor to the Newsletter link on the menu bar of this page. The newsletter will be delivered, initially every two months, as an entry to this blog.

Hopefully we can kindle a lively exchange of experience on everything 3D in astrophysics.

Wolfgang and Nico

Dust in the Milky Way

The cloud distribution on this incredible view of the City of Chicago could be determined by measuring  how they change the light from the street light that they cover. Similarly, stars can be measured to determine the dust distribution in our galaxy. (Image credit: Jim Richardson National Geographic Society)

The cloud distribution on this incredible view of the City of Chicago could be determined by measuring how they change the light from the street light that they cover. Similarly, stars can be measured to determine the dust distribution in our galaxy. (Image credit: Jim Richardson, National Geographic Society, used with permission)

Literally, it is child´s play to get a basic idea of the projected 2D distribution of dust in our galaxy. We took out our son during the summer to explore the night sky and examined the Milky Way. So I mentioned that the dark patches that could be seen were actually dust covering millions of stars in the background. He then easily pointed out other dusty regions. That is the projection on the sky, but what about the 3D structure of the dust? How do we determine the distribution of dark patches along the line of sight? New research using the Pan-STARRS survey applies sophisticated statistics together with stellar and galaxy models to find the structure along the line of sight. As you will see, this is no child´s play at all… Continue reading

I wish all nebulae were expanding homologously

Planetary Nebulae

The end of stars of similar mass as that of the Sun results in nebulae of amazing beauty and variety. Most of them appear to be expanding homologously. Click on image to Judy Schmidt´s Flickr page for the up to 5000×7000 pixel image (used with permission)

When I watch those beautiful 3D animations of nebulae in documentaries or feature films, I always find myself thinking how they figured out the structure of the nebula along the line of sight?

I guess they make an educated guess. But in astrophysics that is usually not enough. For us the key is “homologous expansion”, or contraction, with a hint of symmetry. If all nebulae expanded like that, it would make their 3D reconstruction sooo much easier. In Astrophysics, homologous expansion basically means that the velocity field is such that the shape of the object does not change with time except for a scaling factor. This scaling factor is proportional to time. If that doesn´t make much sense to you and you are tempted to look up the meaning of homologous on Wikipedia or even on the Encyclopedia Britannica, don´t bother, you won´t find it in any relation to astronomy. Then why in heaven is it so important?

Continue reading