Observations¶
Here is a collection of links to papers, with a brief note as to why I found it interesting.
Every few days I hear of new research, driven by the wonderful state of observational astronomy, or rather, observational physics in general.
With all the space and earth based instruments, observational physics is revealing new information almost every day.
There can be a significant time lag in between observations and papers being released.
Many observatories are in the early years of their expected life use, often getting more sensitive over time.
It takes time to get papers reviewed and published.
On the plus side, once a paper is published, it is much less work to repeat the data processing side with more data.
For example, the gravitational wave is expecting the observatories to start a new observational run at the end of 2021.
It will be interesting to see how the sensitivity of the detectors has increased since the last observation run.
Will we see more so called multi-messenger events, gravitational waves accompanied by a gamma-ray burst?
Dwarf Galaxies with big black holes at their centre¶
https://arxiv.org/abs/2111.04770
DYNAMICAL ANALYSIS OF THE DARK MATTER AND CENTRAL BLACK HOLE MASS IN THE DWARF SPHEROIDAL LEO I
M. J. Bustamante-Rosell 1 , Eva Noyola 2 , Karl Gebhardt 2 , Maximilian H. Fabricius 3 , Ximena Mazzalay 3 , Jens Thomas 3 , Greg Zeimann 2
1 Department of Physics, The University of Texas at Austin, 2515 Speedway, Austin, Texas, 78712-1206, USA 2 Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Austin, Texas, 78712-1206, USA 3 Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany
(Dated: November 10, 2021)
ABSTRACT
We measure the central kinematics for the dwarf spheroidal galaxy Leo I using integrated-light measurements and previously published data. We find a steady rise in the velocity dispersion from 300 00 into the center. The integrated light kinematics provide a velocity dispersion of 11.76 ± 0.66 km s −1 inside 75seconds. After applying appropriate corrections to crowding in the central regions, we achieve consistent velocity dispersion values using velocities from individual stars. Crowding corrections need to be applied when targeting individual stars in high density stellar environments. From integrated light, we measure the surface brightness profile and find a shallow cusp towards the center. Axisymmetric, orbit-based models measure the stellar mass-to-light ratio, black hole mass and parameters for a dark matter halo. At large radii it is important to consider possible tidal effects from the Milky Way so we include a variety of assumptions regarding the tidal radius. For every set of assumptions, models require a central black hole consistent with a mass 3.3 ± 2×10 6 M . The no-black-hole case for any of our assumptions is excluded at over 95% significance, with 6.4 < ∆χ 2 < 14. A black hole of this mass would have significant effect on dwarf galaxy formation and evolution. The dark halo parameters are heavily affected by the assumptions for the tidal radii, with the circular velocity only constrained to be above 30 km s −1 . Reasonable assumptions for the tidal radius result in stellar orbits consistent with an isotropic distribution in the velocities. These more realistic models only show strong constraints for the mass of the central black hole.
Einstein’s general relativity withstands double pulsar’s Scrutiny¶
https://physics.aps.org/articles/v14/173
Strong-Field Gravity Tests with the Double Pulsar
Kramer et al.
Phys. Rev. X 11, 041050 (2021)
Published December 13, 2021
See `gotu.spiral`_ module for more information and ideas from this paper.
Microwave background temperature at a redshift of 6.34 from H2O absorption¶
https://doi.org/10.1038/s41586-021-04294-5 Received: 12 February 2021
Roberto Decarli 6 & Roberto Neri 7
Accepted: 30 November 2021
Published online: 2 February 2022
The observation here is a strong absorption line, consistent with water absorption, when redshift is taken into account.
There is a plot of the observed spectrum, in the 70-120 GHz range, which with a redshift of 6.34 correspondsponding to emission frequency in the range 500-900 GHz
The paper seems to be assuming that all the redshift is cosmological and that absorption is happening relatively close to the quasar, so that it is subject to the same cosmological redshift.
The paper proposes a model for the origin of the observed absorbtion lines. The model allows the temperature of the dust to be fitted to observations, giving an estimate of the Cosmic Microwave Background temperature at that distance.
Recall, this is a very high redshift quasar, believed to be at considerable distance.
It is a technique that has been used before on other systems. There appears to be an emerging relation between distance (as determined by redshift) and Cosmic Microwave Background temperature.
What is really happening?¶
The redshift is a combination of cosmological and gravitational redshift.
What if the light leaving the quasar is subject to very significant gravitational red shift explaining most of the redshift?
Our estimate of the power output of the system will be significantly inflated.
There is no reason to assume that dust is not also close to the source of the radiation and as such will likely be warmer than the CMB.
Now if we assume that most of the redshift is gravitational and that these objects are actually quite close, we might expect to find a natural relationship between the mass of the quasar and the temperature of its surrounding water clouds.
In turn, since redshift depends on the mass, there is, presumably a relation between temperature and redshift.
Todo¶
Appendix C of the book has lots of good information on quasars.
Should use this to examine relationship between redshift and temperature.