Active Galactic Nuclei - Science topic

Remark 3.1. Note that if the estimate of the maximum brightness temperature given in [19], is closer to actual values, it would imply Tb;int = 5×1013K. This is difficult to reconcile with current incoherent synchrotron emission models from relativistic electrons, requiring alternative models such as emission from relativistic protons. Remark 3.2. However the proton, as we know, is 1836 times heavier than an electron and absolutely huge energy is required to accelerated it to sublight speed.We argue that these alternative models such as emission from relativistic protons can be suported by semiclassical gravity effect finds its roots in the singular behavior of quantum fields on curved distributional spacetimes presented by rotating gravitational singularities [1], [6]

Following.

Gloria, while I agree with James generally that it is hard for people to empathise with 'inanimate objects', I don't think the issue is quite so black and white.

I think most people have lost interest in what's happening on the Space Station, despite there being humans involved. I'm sure the research done there is important, but there's nothing to see - in a dramatic sense.

By contrast, the photos from the Voyager probes, the images from the Mars Rovers, and the Rosetta/Philae comet rendezvous, I feel, all generated a lot of public interest, because they were all going where no one had been before, showing us better, closer images than available from Earth, and doing things that we previously never thought we could do.

This is an old debate. 'Mere' scientific research will never attract the public interest unless it is something new and exciting. Human missions will, because we can relate to them, personally. It might not be me up there, but it's someone like me, and isn't it incredible that we can do that.

That's what opens the doors to Government funding for all sorts of other space research. People want to see something for their money.

And if we don't put people into space, and open the possibility of living on other worlds, then there are a lot of people out there ready to dismiss all space research as a waste of money - everyone from those who don't want to believe any of it was real in the first place, to the Green lobbies who want to know why we're wasting money on such stuff when the world is in so much trouble.

The "Black Hole" is the “smile” of a Cheshire Cat left behind when the Cat itself has vanished! Any and every cosmic phenomena for official astrophysics and cosmology can be attributed to the mischief of the Cosmic Cats and other such Monsters which are derivatives of one single truth, namely GR. But such an all-encompassing “truth” (like the truth of God) that can be invoked for anything, anywhere, anytime and everywhere, is an ideology and is no truth at all, or is of no use to explain any specific phenomenon!

The absolute truth of official cosmology - a finite and an abstract “spacetime” manifold with tangible physical/mechanical attributes that forms a so-called objective reality of the world; is an axiomatic mathematical fiction and an idealist phantasm that has no basis in material Nature. Please try some other perspectives of objective reality and of the universe: https://www.researchgate.net/publication/320065643_BIG-BANG_CREATED_OR_AN_ETERNAL_AND_INFINITE_UNIVERSE

The “variability problem of active galactic nuclei” and some other cosmic phenomena like GRBs, Gamma Ray Halo, Quasars etc., could be due to random encounter and annihilation reaction of chance accumulated patches (of various sizes, including nebula, stars, globular clusters etc.) of matter and antimatter throughout the galaxies, specially at the core.

A change in sign can only be caused by a change in direction in the line-of-sight magnetic field component at that location. Has the morphology of the jet changed much?

Also given that you only have 3 frequencies it may be also useful to check for any n*pi ambiguities in the chi versus lambda^2 fits which may cause the RM's to vary.

It may be also useful to check the intrinsic polarization angle derived from the RM fits. Check if this changes much over time. The angles should be aligned perpendicular or parallel to the jet in most cases. If the angle varly wildly around the jet it may be a sign of an*pi ambiguities in the fits.

That the best answer I can come up with so far. If I think of something else I'll let you know.

Thank you very much for your answer P. G. Wannier sir. Your suggestions are very helpful.

Sir Franz-Josef Hambsch, I don't have the experimental facility. My work is limited to predicting reaction pathways for the detected (or possible detection) using computational quantum chemistry.  whatever spectroscopy  I need is to understand the papers on the observations of new molecules and the other experimantal works performed on the same systems.

A lot.

Dear Jazeel,

Take a look at this review:

The answer depends on the type of your galaxy. Fig 4 shows that the flux ratio between CO(6-5) and CO(1-0) can vary from 1 for Milky Way to 50 for extreme starbursts and quasars. In order to get this ratio in temperature units you need to divide by the (freq_65/freq_10)^2=36 using the second equation in section 2.4 in this review. Hence, the temperature ratio can take the value from 0.03 to 1.4.

Let me know if anything is unclear.

Cheers,

Michal

The Fermi-LAT experiment has a measurement of the background up to about 0.8 TeV (http://inspirehep.net/record/1322068). Any model of the background at higher energies will be based on this data and catalogs of point sources. For example, http://inspirehep.net/record/1340657.

It is difficult to detect a flux at higher energies because the event rates are too small, and space-based experiments cannot be made with larger volumes, constrained by current rocket technology that would be needed to deploy them.

HAWC is a new ground-based experiment that is currently detecting TeV-scale gamma-rays with a large field-of-view.

You can read these reports

1. A panchromatic view of AGN (Risaliti) http://arxiv.org/abs/astro-ph/0403618

2. Seyfert galaxies in the local Universe (z≤ 0.1): the average X-ray spectrum as seen by BeppoSAX (Dadina) http://arxiv.org/abs/0801.4338

3. Revisiting the Unified Model of Active Galactic Nuclei (Netzer) http://arxiv.org/abs/1505.00811v1

There is so far only one AGN with reported QPOs with high confidence level by XMM-NEWTON: RE J1034+396 (which is published in Nature, astrro-ph:0807.1899).

Then, from citations to the Nature paper, there are several another papers on QPOs in

X-ray band but with much low confidence levels.

This is still very much an open question.

Recent ideas include:

Turbulence in a magnetic field -

Begelman, M. \& Armitage, P. 2014

arXiv:1401.5475

The tearing off of rings from the accretion disk -

Nixon, C. \& Salvesen G. 2014,

MNRAS 437,3994

An older idea is that of magnetically arrested disks (MAD). Here, material initially builds up against a magnetic barrier while in the hard state. When it breaks through, significant mass accumulates close to the black hole, heats up and emits a soft spectrum which outshines the harder power-law component.

e.g. Narayan, Igumenschev & Abramowicz PASJ: Publ. Astron. Soc. Japan 55, L69-L72, 2003

Blazars are among the most polarized astronomical light sources: both the position angle and the fraction of polarized light vary with time for a given object, and studies of polarization variations are much less than those of light intensity variations, so it is still a good field of research with little competition.

Well I think it works pretty well for most (85%) of the cases because it is reasonable. At the same time it fails in the following

(1) the luminosity dependence of the fraction of absorbed objects

(2) the x-ray obscured type 1 AGN (i.e. optically unabsorbed, with broad lines)

(3) the x-ray unobscured type 2 AGN (i.e. optically presenting just narrow lines)

(4) it leads a generation of students to think that all AGN have jets, which might not be the case :)