The Correlation Luminosity-Velocity Dispersion of Galaxies and Active Galactic Nuclei

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Useful and important.  Well written.  A fine and specific conclusion.

My only concern is the relatively large photometric error of 20%.

Author Response

Useful and important.  Well written.  A fine and specific conclusion. My only concern is the relatively large photometric error of 20%.

1. Errors of ~20% are typical for these kinds of measurements, in particular for the Radii and the Velocity dispersions.

Reviewer 2 Report

Comments and Suggestions for Authors

Referee Opinion on the paper The correlation luminosity-velocity dispersion of Galaxies and Active Galactic Nuclei Mauro D’Onofrio , Paola Marziani, Cesare Chiosi, C. Alenka Negre Universe 2932324
The paper is connected with discussion of the correlation between luminosity L and velocity dispersion  observed in different astrophysical contexts. This topic is important in contemporary astrophysics and cosmology, but its presentation by the authors raises significant doubts.
The authors deal with the Faber-Jackson relationship and the text of the work seems to show that the authors treat this relationship as a universal one.
It is true that the authors deal largely with elliptical galaxies for which this relation was introduced. From the text of the paper, it can be assumed that the authors mean this relation, according to them, the active galactic nuclei is also correct, but this has to be guessed and the justification for it is unclear. In reality, however, we are dealing with a much larger number of objects, especially galaxies of late spectral types. For these objects, the Tully Fisher relation, not the Faber-Jackson relation, is appropriate.
The paper does not indicate that the authors demonstrated that “Galaxies of all types share the FJ relation” as it written in conclusion.
Another serious drawback is the fact that the authors assume one specific value of Cosmological parameters as the "Hubble constant" H_0= 70.4 km/ s Mpc. There is still debate around the problem of the correct value of H_0 and it is therefore better to use the dimensionless parameter h=H_0/100 km/ s Mpc which will facilitate comparison of the results of the work with its possible successors using different values of cosmological parameters.
In my opinion, all these points need to be clarified and corrected before any substantive consideration can be given to accepting or rejecting the paper for publication.

Author Response

Referee Opinion on the paper The correlation luminosity-velocity dispersion of Galaxies and Active Galactic Nuclei Mauro D’Onofrio , Paola Marziani, Cesare Chiosi, C. Alenka Negre Universe 2932324

The paper is connected with discussion of the correlation between luminosity L and velocity dispersion s observed in different astrophysical contexts. This topic is important in contemporary astrophysics and cosmology, but its presentation by the authors raises significant doubts.
The authors deal with the Faber-Jackson relationship and the text of the work seems to show that the authors treat this relationship as a universal one.
It is true that the authors deal largely with elliptical galaxies for which this relation was introduced. From the text of the paper, it can be assumed that the authors mean this relation, according to them, the active galactic nuclei is also correct, but this has to be guessed and the justification for it is unclear. In reality, however, we are dealing with a much larger number of objects, especially galaxies of late spectral types. For these objects, the Tully Fisher relation, not the Faber-Jackson relation, is appropriate.
The paper does not indicate that the authors demonstrated that “Galaxies of all types share the FJ relation” as it written in conclusion.

 

1. We agree that the Tully-Fisher relation is generally used when dealing with Early-Type Galaxies (ETGs). However, simulations, that do not give indication on the morphological types, provide a well defined Fabr-Jackson relation down to very low massive galaxies. We do not use real LTGs in our sample, only simulated galaxies, so our conclusion refer only to that. We updated the text accordingly.

Another serious drawback is the fact that the authors assume one specific value of Cosmological parameters as the "Hubble constant" H₀= 70.4 km/ s Mpc. There is still debate around the problem of the correct value of H₀ and it is therefore better to use the dimensionless parameter h=H_0/100 km/ s Mpc which will facilitate comparison of the results of the work with its possible successors using different values of cosmological parameters.
In my opinion, all these points need to be clarified and corrected before any substantive consideration can be given to accepting or rejecting the paper for publication.

 

1. The current tension on H₀ is between 68 Km/s Mpc (Planck measurment) and 72 (SNe and others distance indicators) . Our adopted value of 70 km/s Mpc is exactly in between. We do not think it is necessary to make new figures using h. By the way the only difference is that of producing small differences in the effective radii, withou changing the shape of the correlations.

Reviewer 3 Report

Comments and Suggestions for Authors

The article is interesting as it discusses the various aspects of the Faber-Jackson relation regarding AGNs and early type glaxies. The article could be published after minor revision (details below).

My questions:

1.) The sentence between  the lines 87-89 is not clear (at least for me): if the dimensioness accretion rate is low, why would the Eddington ratio approach unity? Please clarify it.

2.) Line 103. Please add Sect. number.

3.) Lines 135-140: Citing Bernardi et al. the authors emphasize that fitting the log L = a log sigma +b relation will give different correlation than the log sigma = a' log L +b' relation. Beeing linear the depenedence from pure statistical point of view the two should give the same level correlation. Please specify why in this case could this two fitting be different.

4.) Lines 217-225: How the discussed L(Hbeta)-sigma relation is dependent on the redshift?

5.) Lines 287-288: it mentions that the redshift data is also used in the analysis. When the photometric erros are in the range of 20%, how big deviation could be caused  by the redshift range of 0-0.07 (line 280)?

6.) Line 398: Eq. 3 is quite ugly.

7.) Page 16., Fig. 5.: what is the line? It is the fitting or it is the equality?

8.) I think the Sect. 4.8  (lines 650-709) is not ready for publications in its present form. This section should be more focused and more precise, needs more work. Regarding the section my problems are:

-       8.1.: Line 655: the numbering of the figures usually will go with the article: however here the numbering is ad hoc mixed. E.g.  Fig. 13. appears here first, while Fig. 12. comes later only. Also the text incorrectly mentions the middle panel of Fig. 13., which contains 2 sub-figures. The middle panel expression repeats later.

-       8.2: Fig.8.: what are the lines? Were the outliers left out during the fitting, or the full data were used (including e.g. the bottom plot's (~1600,~2.8) point , which seems to be an outlier)?

-       8.3: Figs. 9 and 11. are the same plots, it is clearly an error!

-       8.4: Figs. 11. caption: what are the color codes?

-       8.5: Figs. 13 and 14: the labels on the axes are too small.


9.) On Fig. 7. top-left figure the theta distribution is shown for the directions: how consistent are this  data with a belief that the directions should be isotropic?

10.) On Fig. 10. top panel: above z>0.6 there's a group of data significantly below the fitted curve. Please discuss how it effects the fit.

11.) Fig. 15 top right panel: there's a difference in the slope between the AGN and the ETG observations. What is causing this effect?


Yours sincerely,
          

Author Response

The article is interesting as it discusses the various aspects of the Faber-Jackson relation regarding AGNs and early type glaxies. The article could be published after minor revision (details below).

My questions:

1.) The sentence between  the lines 87-89 is not clear (at least for me): if the dimensioness accretion rate is low, why would the Eddington ratio approach unity? Please clarify it.

1. Done

 

2.) Line 103. Please add Sect. number

 

1. Done

3.) Lines 135-140: Citing Bernardi et al. the authors emphasize that fitting the log L = a log sigma +b relation will give different correlation than the log sigma = a' log L +b' relation. Beeing linear the depenedencefrom pure statistical point of view the two should give the same level correlation. Please specify why in this case could this two fitting be different.

1. Bernardi et al. (2003) reported the correlation coefficients obtained with the bi-spline X-Y and Y-X fitting. The degree of correlation is the same, but the coefficients change.

 

4.) Lines 217-225: How the discussed L(Hbeta)-sigma relation is dependent on the redshift?

1. Done

 

5.) Lines 287-288: it mentions that the redshift data is also used in the analysis. When the photometric erros are in the range of 20%, how big deviation could be caused  by the redshift range of 0-0.07 (line 280)?

 

1. For ETGs only data at redshift ~0 are used. There are no systematic differences for the radii in the redshift interval since we always used the luminosity distance to calculate them.

6.) Line 398: Eq. 3 is quite ugly.

 

1. R. Done

7.) Page 16., Fig. 5.: what is the line? It is the fitting or it is the equality?

1. Both. The best fit line overlies the line of equality (dot-dashed). The latter is therefore not visible. A sentence explaining this has been added in the caption

 

8.) I think the Sect. 4.8  (lines 650-709) is not ready for publications in its present form. This section should be more focused and more precise, needs more work. Regarding the section my problems are:
-       8.1.: Line 655: the numbering of the figures usually will go with the article: however here the numbering is ad hoc mixed. E.g.  Fig. 13. appears here first, while Fig. 12. comes later only. Also the text incorrectly mentions the middle panel of Fig. 13., which contains 2 sub-figures. The middle panel expression repeats later.
-       8.2: Fig.8.: what are the lines? Were the outliers left out during the fitting, or the full data were used (including e.g. the bottom plot's (~1600,~2.8) point , which seems to be an outlier)?

 

1. The lines are unweighted least square fits, and the outlier were included. As a matter of fact, in each panel there is just one object that may be consired as outlier, as pointed out by the referee. This datum has however no significant effect on a fit over ~ 100 objects.

-       8.3: Figs. 9 and 11. are the same plots, it is clearly an error!

 

1. We apologize for this confusion. In the revision, we have carefully checked the order of the figures and rearranged them according to the order of citation in the text.

-       8.4: Figs. 11. caption: what are the color codes?

 

1. Blue are for Pop. A not xA, magenta for xA. This explanation has been added in the caption

-       8.5: Figs. 13 and 14: the labels on the axes are too small.

 

1. We have remade the plots enlarging the labels.

9.) On Fig. 7. top-left figure the theta distribution is shown for the directions: how consistent are this  data with a belief that the directions should be isotropic?

1. If the distribution is assumed isotropic we expect P(θ)dθ ~ sinθdθ. A trend like this seems to be followed up to sinθ≈0.4, meaning θ≈23. For larger θ, the detection of the sources – and their inclusion in clor based surveys – might be disfavored by the anisotropic emission of the geometrically thick torus that is expected in sources accreting at super-Eddington rates, and by the presence of a dusty obscuring torus that would suppress the view of the BLR at angles θ≳45, according to the unification schemes.

 

10.) On Fig. 10. top panel: above z>0.6 there's a group of data significantly below the fitted curve. Please discuss how it effects the fit.

1. The group of sources below the prediction for the ΛCDM model at z~0.6-0.7 is affecting strongly the fit, as shown in the middle and bottom panel. It may a bias due to the selection of objects preferentially nearly face-on oriented. We briefly mention this effect in the revised version,

 

11.) Fig. 15 top right panel: there's a difference in the slope between the AGN and the ETG observations. What is causing this effect?

 

1. The radii derived for the AGN sample are quite different from the effective radii derived for galaxies. The radii likely do not reflect the area containing half the total luminosity as it is the case for ETGs.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors   Second Referee Opinion on the improved version the paper The correlation luminosity-velocity dispersion of Galaxies and Active Galactic Nuclei Mauro D’Onofrio , Paola Marziani, Cesare Chiosi, C. Alenka Negre Universe 2932324       Unfortunately, the authors did not take into account the reviewer's comments in the revised version. It is true that they wrote an explanation regarding point one, but it is not reflected in the amended text, and what is worse, it seems to be inconsistent with what follows from the original text. The work is still written vaguely and one has to guess what the authors may have in mind.As for point 2, I fully maintain my opinion, which the authors also did not take into account. Meanwhile, the problem is broader than just the issue of correlation coefficients (and the authors - quite rightly - do not limit themselves to them). Moreover, the issue of the value of H_0 is not resolved and the discrepancies in this matter are significant (which the authors admit, rightly writing about "current tension on H_0")      Since I believe that my comments from the first review are important and their consideration is necessary for the publication of the work, this is not the time to analyze the remaining corrections made by the authors in the revised version and I am forced to recommend rejection of the article in its current form.

 

          

 

Author Response

please see the attachment.

Author Response File: Author Response.docx