Extragalactic Astronomy - Science topic

According to the paper below❌ then one could well guess-speculate that the brightest and oldest QUASARs that we observe today are the result of mega collisions between numerous galaxies in formation and with central hypermassive black holes. Mega-collisions occurred at the dawn of the formation of galaxies, when the size of the Universe was much smaller than the current one (high density of the galaxies themselves). This would have created such colossal black holes very early that today they would represent a completely different entity from the common hyper-massive black holes. Would these immense black holes, all extra-galactic, be the size of a medium-small sized Galaxy??

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ABSTRACT

The triggering mechanism for the most luminous, quasar-like active galactic nuclei (AGN) remains a source of debate, with some studies favouring triggering via galaxy mergers, but others finding little evidence to support this mechanism. Here, we present deep Isaac Newton Telescope/Wide Field Camera imaging observations of a complete sample of 48 optically selected type 2 quasars – the QSOFEED sample (⁠L[OIII]>108.5L⊙

⁠; z < 0.14). Based on visual inspection by eight classifiers, we find clear evidence that galaxy interactions are the dominant triggering mechanism for quasar activity in the local universe, with 65+6−7

per cent of the type 2 quasar hosts showing morphological features consistent with galaxy mergers or encounters, compared with only 22+5−4

per cent of a stellar-mass- and redshift-matched comparison sample of non-AGN galaxies – a 5σ difference. The type 2 quasar hosts are a factor of 3.0+0.5−0.8

more likely to be morphologically disturbed than their matched non-AGN counterparts, similar to our previous results for powerful 3CR radio AGN of comparable [O III] emission-line luminosity and redshift. In contrast to the idea that quasars are triggered at the peaks of galaxy mergers as the two nuclei coalesce, and only become visible post-coalescence, the majority of morphologically disturbed type 2 quasar sources in our sample are observed in the pre-coalescence phase (61+8−9

per cent). We argue that much of the apparent ambiguity that surrounds observational results in this field is a result of differences in the surface brightness depths of the observations, combined with the effects of cosmological surface brightness dimming.

CONCLUSIONS

Our deep imaging observations of nearby type 2 quasars provide strong evidence that galaxy interactions are the dominant triggering mechanism for quasars in the local universe, consistent with the results for other samples of nearby radio-loud and radio-quiet quasars that have been observed to a similar surface brightness depth. Much of the apparent ambiguity of the results in this field is likely to be due to differences in the surface brightness depths of the observations combined with the effects of cosmological surface brightness dimming. Clearly, it is important that these factors are given full consideration in future studies of quasar triggering.

Beyond the dominance of galaxy interactions, there appears to be a wide range of circumstances under which luminous, quasar-like AGN are triggered. Although our results indicate that the gas flows associated with galaxy interactions can provide sufficient mass infall rates to the central SMBH to trigger quasar activity even well before the two nuclei have coalesced, some objects are triggered in a post-coalescence phase. Moreover, a minority of our sample are disc galaxies that appear undisturbed in deep imaging observations. Therefore, secular processes may sometimes be capable of triggering quasar activity, even if this is not the dominant mechanism at low redshifts.

Extraterrestrial life is hypothetical life which may occur outside Earth and which did not originate on Earth. Such life might range from simple prokaryotes (or comparable life forms) to intelligent beings and even sapient beings, possibly bringing forth civilizations which might be far more advanced than humanity. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life in all its forms is known as astrobiology. https://en.m.wikipedia.org/wiki/Extraterrestrial_life

IEEE Spectrum January 2021 (attached) p. 30 - 31 (32-33)

The James Webb Space Telescope will let us see back almost to the big bang!!!

The concept of the finite universe or an universe limited in apace and time is due to the limitation of any epistemology based on causality for which there has to be a first cause of a beginning. Idealized mathematics promoted by the Platonists and the rationalists is the epitome of causality based epistemology and cosmology.

Albert Einstein adopted Platonic mathematical idealism in modern physics after the breakdown of causality with the discovery of the revolutionary quantum phenomena. But mathematics is helpless to deal with the concept of the Infinite as Cantor found out. Einstein’s theories of relativity, specially GR that is the basis of modern official cosmology, necessarily started with the presupposition that the universe must be finite; but this is a wishful thinking just for the convenience of his mathematical approach to epistemology and cosmology!

Einstein’s theories of relativity are invalid and have no place in an infinite universe. And the universe IS infinite! Please see the links below:

Recently, there has been calls in RG for medieval type Inquisition to deal with the growing number of scientists who doubt or even deny the validity of Einstein’s theories of relativity. The following forum is an example:

But the relativists, Crusaders and the Inquisitors of official physics in RG have now already been silenced through the power of logic and science alone:

I am not sure what to understand under term "colonize". Mars is a smaller planet than Earth, but it is still very huge object and pretty far away - and our present technology has difficulties even to land there by robots (though NASA is the best). So far there is no achievement to send a robotic probe that would be able to land there and return back to Earth... And we are ready to discuss about the colonization. What about "colonization", let's say, 10% of Sahara? We have lot of people for manpower, food, water supply, health care, good air to breathe, million tons of heavy construction equipment... If you mean to make "Mars habitable for humans" I am very skeptic, mother Nature is much-much stronger (will we make breathable atmosphere ? will we make artificial magnetic field to protect atmosphere against solar wind erosion?, etc...) Mars - perhaps for robots... For humans, top task is to save the Earth...

Dear Thierry!

You are right insofar, that every galaxy has an anisotropic gravitational field. It is caused by the mass distribution evoked by rotation movement. Only in a very high distance you can calculate with a single (or simple) mass centre.

A star cluster, which arised par example in the peripery will be deformed by different rotation speeds, gravity and delay. It leads to the spiral shape. (The delay is an issue of a paper I am working on.)

My point is that galaxies are going through a cyclic development. We can observe different states of this development respectively the different states of activity.

@M. Cerviño: I am astonishing about the pictures of early galaxies maybe before 12billion years. They show the same shape as current galaxies. Is this not a contradiction to the big bang theory?

Hans

Please read the paper, may be helpful for you.  A new approach to the correction of

Indeed, the energy coming from the parent star controls the composition, the temperature and the circulation of the atmosphere, which are in fact coupled. To study the circulation in exoplanet atmospheres, you can use a GCM-type model (Global Climate Model). You will find useful references in the paper quoted above. 

I should probably start by saying that the very Physics behind the occurrence of the "stiff" and "soft" equations of state is quite complicated. You can subdivide the EOS into regions: I. Nuclear saturation density; II. Supra-saturation nuclear density. Now for each case the stiffness/softness comes from two main ingredients: (a) EOS of symmetric nuclear matter; (b) EOS of pure neutron matter --> this one can be replaced by the nuclear symmetry energy. Now we can talk about the Physics behind the stiffness/softness for each case:

I. (a) The stiffness/softness is mostly controlled by the incompressibility parameter that can be more or less constrained by nuclear breathing modes. There are no big variations (for example it is well constrained to be about 200 < K < 260 MeV)

I. (b) The stiffness/softness is due variation of the nuclear symmetry energy. The large uncertainty comes from our poor knowledge on isovector channel of nuclear interaction. Physics of exotic nuclei close to dripline contain this information, however they are not yet readily available. This is a hot topic of research.

II. (a) The stiffness/softness is controlled by the skewness parameter (third derivative of energy per nucleon). The physics of finite nuclei is not sensitive to this variation, and therefore one can have models giving ranges of the EOS with maximum NS mass from 2 to 3 solar masses.

II. (b) Density dependence of the symmetry energy at suprasaturation is basically unknown. That is why we have a huge variations in the EOSs. 

I suggest you to further read this and references therein: https://www.researchgate.net/publication/232238087_Constraining_the_High-Density_Behavior_of_Nuclear_Symmetry_Energy_withthe_Tidal_Polarizability_of_Neutron_Stars

Well for tensorial quasi normal modes (Gravitational Waves) we have interferometers LIGOs working in advanced state, but just isolated QNM will not be easy to find, but if this happens after the coalescing compact binaries (higher mass loss), it might be seen. 

The discovery of the accelerating expansion of the Universe is a milestone for

cosmology, as significant as the discovery of the minute temperature variations in the

Cosmic Microwave Background (CMB) radiation with the COBE satellite (Nobel Prize

in Physics 2006, John Mather and George Smoot). By studying the CMB, we may learn

about the early history of the Universe and the origins of structure, whereas the

expansion history of the Universe gives us insights into its evolution and possibly its

ultimate fate.

The expansion of the Universe was discovered by Vesto Slipher, Carl Wirtz, Knut

Lundmark, Georges Lemaître and Edwin Hubble in the 1920’s. The expansion rate

depends on the energy content – a Universe containing only matter should eventually

slow down due to the attractive force of gravity. However, observations of type Ia

supernovae (SNe) at distances of about 6 billion light years by two independent research

groups, led by Saul Perlmutter and by Brian Schmidt and Adam Riess respectively,

reveal that presently the expansion rate instead is accelerating.

Within the framework of the standard cosmological model, the acceleration is generally

believed to be caused by the vacuum energy (sometimes called ”dark energy”) which –

based on concordant data from the SNe, the observations of the anisotropies in the CMB

and surveys of the clustering of galaxies – accounts for about 73% of the total energy

density of the Universe. Of the remainder, about 23% is due to an unknown form of

matter (called ”dark matter”). Only about 4% of the energy density corresponds to

ordinary matter like atoms.

In everyday life, the effects of the vacuum energy are tiny but measurable – observed

for instance in the form of shifts of the energy levels of the hydrogen atom, the Lamb

shift (Nobel Prize in Physics 1955).

The evolution of the Universe is described by Einstein’s theory of general relativity. In

relativistic field theories, the vacuum energy contribution is given by an expression

mathematically similar to the famous cosmological constant in Einstein’s theory. The

question of whether the vacuum energy term is truly time independent like the

cosmological constant, or varies with time, is currently a very hot research topic.

source:THE aCCELERATING UNIVERSE

compiled by the Class for Physics of the Royal Swedish Academy of Sciences

Hi Somak,

  as far as I know, there hasn't been work (within the collaboration) on specific spectral features since BPZ uses templates. I'd say that depending on the spectral type of the galaxies and their redshift, the most informative feature will change. Therefore, using templates avoid biases related with putting too much weight to specific features.

  With respect to previous multifilter surveys, like COMBO17, I would say that what made very powerful the J-PAS filter system is that the design of the filters has been done from scratch to maximize the photo-z determination (this is explained in Sect.2 of the document). The result is that the filters are narrow (145A), almost top hat with no wings, and there is no gaps between them, covering the whole optical range.

  For any further information about J-PAS, please don't hesitate to contact me or any member of the collaboration.

  Cheers!

Hi Somak,

  the description of the data in the catalogues can be found in Molino et al.(2014) paper:

  If you have doubts about the content of the catalogues, I would suggest to contact directly the first author (Dr. Alberto Molino).

  Regarding the public images, you are right, they are indeed the synthetic F814W images reconstructed from the narrow band images. The way in which they have been constructed is also explained in Molino et al.(2014).

  Finally, with respect to the NIR images, I'll try to find out whether they will be made public.

Cheers!

I also suggest a recent paper - http://arxiv.org/abs/1212.5317.

To complete a bit the excellent answers given before, once Gaia is finished, we will need to go on observing Solar System objects, even if the precision of the observations we obtain are lower than those of Gaia.

Gaia observations will not have an infinite precision, and will be biaised, like any instrument. Because of these errors and uncertainties, the accuracy of the ephemeris obtained will be limited in time. The positions obtained for the observation time-span will be very accurate, and will begin to degrade with time once we do not observe the bodies anymore. This is how some irregular satellites of Jupiter and some asteroids are now considered as lost: we haven't observed tham for a long time, and their real position is now far from the one given by the dynamical models used. In fact, for long-term accuracy, it is better to have a long time span with less precise observations, than a very short time span of precise observations.

So, for Solar System objects, Gaia will definitely not be the end of observations, but a much needed step toward mas/submas accurate ephemeris.

I would say that the gravity-dependence of chemical reactions can be neglected for two reasons:

1) the enthalpy has to be used with a little bit carefullnes in this context. The enthalpy is defined as the energ content of thermodynamical systems. However, this holds for every system, regardless of the occurence of a chemical reaction. If you want to study chemical reactions, you have to use the change of enthalpy dH. This is defined by: dH = TdS + V dp (T being the absolute temperature, dS the change of entropy and V the volume). If you work at constant pressure dp = 0. This is mostly the case, as you have no pressure variation for solids and nearly no variation in liquids or gases (as long as you are not dealing with very large volumes (i.e. some km³ or so).

and, even more important

2) all chemical reactions are driven by the electrons, or, more generally, by electric forces between charged particles. As the electric force between, say, an electron and a proton, is around forty! orders of magnitude stronger than their gravitational force, one can immediately see that gravitation is neglible compared to electrical forces.

Oh this was a fantastic answer Paul. I was trying to understand

this redshift for last few months but never had enough time to

dig into the literature.

Heleri,

Sorry I don't think I answered the question you asked which perhaps implied that the B-mode signal was non-Gaussian. It is Gaussian but not covered by the purely temperature angular power spectrum (TT) as they are part of the polarized fields which are E and B. These E and B distributions can also be described by spherical harmonics which are uncorrelated and random just like the temperature distribution and so are Gaussian.

The EE signal was seen by DASI several years ago, but is caused by the local temparature isotropy scattering differently into different linear polarizations when the Universe became transparent. Just to complicate matters this causes correlations between T and E due to this scattering process off electrons, which has also seen. This is still Gaussian

It's the handedness or parity of the gravitational waves which causes the special spiral B-mode pattern in polarization everyone is looking for.

Pulsar observers will tell they saw indirect evident of gravitational waves, but very indirect in my point of view. Seeing the run down rate of a fast binary pulsar orbit (PSR 1913+16) consistent with gravitation radiation emission rate via General Relativity.

Yes, I understand now. Putting r=R, the criitcal value of C actually equals 2 radians, i.e. about 115 degrees.

Try this - its old , but was pretty deep

but there are several more recent CCD based surveys as well

Examples are the reflection nebulae around the stars of the Pleiades.