Questions tagged [quasars]

Questions about quasi-stellar radio sources, active galactic nuclei that are far away and quite old.

Filter by
Sorted by
Tagged with
4 votes
2 answers
391 views

On the "periodic" lightcurves of Active Galactic Nuclei

So apparently they are all lightcurves of (likely candidates) Active Galactic Nuclei and in some way or the other they all appear to be periodic: I'd like to know the reason for this and the ...
10 votes
2 answers
2k views

What is the mechanism through which mass is converted to thermal energy in the accretion disc of a black hole?

In the book The Cosmic Perspective, it is stated that as matter is falling into a supermassive black hole, up to $40\%$ of its mass are converted to thermal energy, making the accretion of matter ...
0 votes
0 answers
41 views

Trying to understand how to properly implement this equation to a healpix map

So i am working on reproducing a paper (Secrest, N. J., von Hausegger, S., Rameez, M., Mohayaee, R., Sarkar, S., & Colin, J. (2021). A test of the cosmological principle with quasars. The ...
16 votes
5 answers
7k views

Why are all quasars so far away?

Why are all quasars so far away? If the universe is homogeneous, we should expect to have a homogeneous distribution of quasars, but all of then seem to be far away from Earth. Why is that?
3 votes
0 answers
37 views

What "external illumination" source causes the heating of a quasar's accretion disc?

In Section 3.4, UV-to-optical continuum flux ratio, Gaskell et al. (2023) Estimating reddening of the continuum and broad-line region of active galactic nuclei: the mean reddening of NGC 5548 and the ...
2 votes
2 answers
176 views

Reduced chi square value

I am currently plotting a continuum of observed data. I need to check the effectiveness of the fitted continuum with the reduced chi-square method. Ideally, should the reduced chi-square value ...
1 vote
0 answers
28 views

Are there any experiments or observations indicating that the Hubble flow can influence AGNs, quasars and galactic winds (outflows)?

Galactic winds (or outflows) are produced by AGNs (Active Galactic Nuclei), quasars, supernovas...etc which basically eject matter usually in form of waves or spheres, sometimes even arriving to the ...
3 votes
1 answer
62 views

Can the Hubble expansion inject energy in AGN and quasar outflows?

I found this article about the behavior of quasar outflows in cosmology and how they can create a magnetic field. In section 2.1.4., the authors say that when a quasar produces a "wave" or ...
12 votes
2 answers
4k views

What happens when the quasar remnants reach Earth in 3 million years?

According to this article, during: (during) a quasar stage in its evolution (6 million years ago) ... the Milky Way’s central black hole swallowed a huge amount of gas, creating a shock wave that has ...
9 votes
1 answer
572 views

What does "Effective radius of [CII] line is 1.4 kpc" mean?

A recent paper (A dusty compact object bridging galaxies and quasars at cosmic dawn) describes one of their results as the "Effective radius of [CII] line" (Extended Data Table 2, p38): I ...
2 votes
1 answer
412 views

Could life develop in a galaxy with a quasar at its centre?

Quasars are a type of Active Galactic Nucleus that inhabit the centres of some galaxies. They are among the most energetic objects known in the universe, emitting up to a thousand times the energy ...
5 votes
1 answer
124 views

Sudden spikes on the light curve of a Quasar from K2 mission

I obtained the optical light curve of 3C 273 QSO from the MAST repository off the K2 mission and plotted it by making the FITS into a CSV file through Pandas dataframe and plotting the obtained ...
2 votes
1 answer
133 views

How to convert spectra to log-wavelength and interpolate them into linear spacing in log-wavelength

I want to write a function that cross correlates a spectrum with a quasar template I’d like to ask you how can I convert my flux density vs wavelength spectrum to log-wavelength. It’s not clear to me ...
4 votes
2 answers
151 views

How to interpret this spectrum of the "new DESI Quasar at z = 6.53"; what causes the big edge at about 9150 Angstroms?

I'm not exacty sure why but Scitech Daily's Seeing Dark Energy’s True Colors: DESI Creates Largest 3D Map of the Cosmos includes the graphic and caption below. It indicates a quasar in a Hubble image ...
3 votes
1 answer
121 views

Intergalactic Lyman-alpha absorption for high redshift quasars (Gunn-Peterson effect)

This is a follow up to a recent question on SE asking about the apparent suppression of radiation shortward of the (red-shifted) Ly-$\alpha$ line of a quasar at redshift $z=6.53$. The general ...
1 vote
2 answers
202 views

Is there an official list of objects in the sky?

I would like to know how many known quasars there are in the Universe as well as x-ray binary black holes (not Neutron stars) but I don't seem to be able to. I also want to know how many black holes ...
2 votes
2 answers
140 views

Could quasars be interior to the event horizon of a SMBH?

My question is prompted by suspicion of three current ideas in astrophysics: GR predicts a singularity at the center of a BH without regard to QM. quasar hyper-luminosity is caused by an acretion ...
2 votes
1 answer
53 views

Obtaining the Flux-Time plot for a Quasar

As a follow up question to Obtaining the Light curve of a a Quasar, I wish to know how to obtain a Light curve for a quasar observation like this data set over here. Is there an archival repository ...
3 votes
1 answer
74 views

Obtaining the Light curve of a a Quasar

So, I am relatively comfortable with handling $\textit{FITS}$ files and hence I choose Python for the following operation. The thing is that I need to analyse some Quasar light curves and hence I went ...
2 votes
1 answer
566 views

What does "TON" in TON 618 stand for?

I don't think TON 618 is a random name, but rather a composition of category name and a number. But when I tried to google it, any article about TON 618 did not contain anything about its name origin ...
4 votes
1 answer
299 views

Is quasar 2M1310-1714 outside the observable universe?

This Einstein ring Image credit: NASA / ESA / Hubble / T. Treu / Judy Schmidt shows multiple images of the quasar 2M1310-1714. Its distance is quoted at 17 billion light years and although the age ...
6 votes
1 answer
104 views

Why are the radio images of the jet of 3C 273 different?

At NASA/IPAC Extragalactic database, we can see images of the jet of matter being ejected from the quasar 3C 273. Here are a couple from the radio spectrum as examples: My question is: why are the ...
-1 votes
2 answers
58 views

How can I find more information on a certain galaxy when NED isn't helping?

The paper High Frequency Peakers: Young radio sources or flaring blazars? by S.Tinti et.al. lists some nice radio-wavelength SEDs, like these for instance: When looking for more photometric info on a ...
2 votes
1 answer
54 views

Radio SEDs for quasars

Using data from https://ned.ipac.caltech.edu/, I can get nice-looking spectral energy distributions for quasars, such as for these two: but most of their points are in UV to IR range. I'm looking ...
4 votes
2 answers
125 views

How much light comes from quasars in an AGN?

From what I've been able to gather, the very bright spot at the center of galaxies is produced by both the central quasar and a dense cluster of millions of stars that surround it. How much of the ...
3 votes
0 answers
162 views

Number of obscured AGN compared to unobscured AGN

Urry and Padovani 1995 proposed a unified model for Active Galactic Nuclei, which has since been recognised as a good model for AGN. If AGN are randomly oriented, then I'd expect there to be more ...
4 votes
1 answer
179 views

Why do Seyfert Galaxies emit less energy than Quasars and Blazars, and how is the emitted energy measured?

When I was reading information about QSOs on a website, it said that Seyfert Galaxies emit less energy than Quasars and QSOs. Why do Seyfert Galaxies emit less energy than quasars, and how is this ...
6 votes
1 answer
119 views

3C273 jet mass estimate

In this picture of 3C273, we can see a jet—estimated to be around 200,000 light-years long—being emitted. I'm trying to find an estimate for the mass of the jet. It's a stream of ...
2 votes
0 answers
79 views

Can Quasars generate Heavy Elements?

Pretty sure Quasars were involved in increasing Galactic metallicity but is there evidence of quasar AGN's generating heavy elements, such as radioactive ones and shooting them across the universe in ...
2 votes
0 answers
85 views

How does hawking radiation work without virtual particles?

How does hawking radiation work without the existence for virtual particles? I read that certain quantum fields are distorted when a black hole forms on top of them. But what fields specifically? If ...
2 votes
1 answer
124 views

How do accretion disks around black holes evaporate via winds?

I'm curious as to how accretion disks around black holes evaporate. I've heard winds play a crucial role in this. But what winds specifically and how do they form? Is it a stellar wind of sorts? If so ...
4 votes
2 answers
502 views

Are quasars simply AGNs that are viewed from a particular angle?

I found the picture below in an answer to the post "Was the Milky Way ever a quasar". The picture is published on a website belonging to "NASA/IPAC Extragalactic Database". In the answer that has 16 "...
1 vote
1 answer
221 views

In the 1950's how were radio-astrometric positions with portable dishes so precise they could be assigned to their dim optical counterparts (Quasars)?

In my question Why are quasars so far away that they couldn't be optically resolved in the 1950's? I included the following short paragraph, but then added strikethrough to the second sentence ...
3 votes
2 answers
315 views

Why would the merger of spinning black holes within the accretion disk of a supermassive black hole cause them to "shoot straight up" out of the disk?

I just tried to read the new New York Times article Two Black Holes Colliding Not Enough? Make It Three which links to the new 25-June-2020 Physical Review Letter Graham et al. Candidate ...
3 votes
1 answer
363 views

Why are quasars so far away that they couldn't be optically resolved in the 1950's? [duplicate]

Wikipedia's Quasar includes the following in its introduction: The term quasar originated as a contraction of quasi-stellar (star-like) radio source, because quasars were first identified during the ...
2 votes
1 answer
187 views

What enhances the capture and merge rates of pairs of small black holes orbiting around supermassive black holes?

I just tried to read the new New York Times article Two Black Holes Colliding Not Enough? Make It Three which links to the new 25-June-2020 Physical Review Letter Graham et al. Candidate ...
6 votes
1 answer
929 views

Is there a recent update on the mysterious M82 radio source reported in 2010?

The Wikipedia page on the "Cigar Galaxy" (M82) has the following summary about an "unknown object": In April 2010, radio astronomers working at the Jodrell Bank Observatory of the University of ...
2 votes
0 answers
71 views

How to model blazar light curves

I have SED data spanning over a couple of days and I'm able to find the parameters of the SED (R, B, break energy,...) using least squares method. My question is how to model light curves (with t_acc, ...
5 votes
1 answer
980 views

Redshift quantization

A full disclosure to begin with: I'm a PhD student in mathematics and while I understand most of standard cosmological-astronomical terms and I've followed a one semester course on cosmology, I don't ...
7 votes
1 answer
561 views

How bright would Sagittarius A* be from Earth if it became an Active Galactic Nucleus?

Essentially I'd like to know how bright our central black hole could appear from earth in relation to full moon brightness. Assuming maximum energy output (like when it's gobbling up an entire ...
3 votes
1 answer
997 views

How to convert luminosity at rest frame wavelength of 1450 A to absolute magnitude at 1450 A?

How do I convert the luminosity (erg sec$^{-1}$ Hz$^{-1}$) of a quasar at a rest frame wavelength of 1450 Angstroms to absolute magnitude at the same wavelength? I know that the bolometric ...
1 vote
0 answers
39 views

Absorption line in quasar spectrum

I have quasar spectrum which includes emission and absorption lines. I need to find absorption lines in between 2 wavelength. How can I do it with coding?
2 votes
3 answers
187 views

light emission of quasars

I'm studying Astrophysics and I have some video's from a past course. I'm currently studying the reionization of the universe. At the current point in the class, the instructor is talking about ...
9 votes
1 answer
368 views

How are neutrinos produced in blazar jets?

I was watching the press release about measuring neutrinos and gamma rays from a distant blazar. One of the presenters mentioned that the neutrinos are associated with very high energy protons caught ...
4 votes
0 answers
343 views

Why the space is so dark even there are billions of stars and many quasars emitting light [duplicate]

In our galaxy itself, there are millions of stars, and there are many more other galaxies in our local group and billions in the observable universes. For sure they all emit a lot of light, still why ...
2 votes
1 answer
437 views

Do gravitationally bound (e.g. orbiting) objects really resist the expansion of space?

Thinking about the expansion of space, it is commonly explained that gravitationally bound objects (like galaxies and galaxy clusters) will not be affected by the expansion of space (dark energy). I ...
1 vote
1 answer
115 views

Regions and size of an AGN

In this diagram of the regions and approximate scale of an AGN: which is from this paper, what do the x and y scales log(z/pc) and ...
2 votes
2 answers
1k views

What is projected separation and how can I make sense of its unit (h^-1 kpc)?

I have been reading this paper on the separation of a binary quasar in which it states: At a projected separation of 8.3/h kpc (Omega_matter = 1), CTQ 839 would be the smallest projected separation ...
1 vote
0 answers
49 views

What compounds are present in 3C273?

Anyone know if we have any chemical reactions occuring in this quasar?
1 vote
0 answers
53 views

Causes of emission of accretion disk

As far as I can see, there are two main sources for the emission of energy from an accretion disk: release of gravitational potential energy of the infalling matter; friction from differential ...