Report on Włodzimierz Godłowski`s habilitation thesis 1 Thesis 2

Report on Włodzimierz Godłowski's habilitation
thesis
B.F. Roukema
31 grudnia 2012
1
\
Thesis
Godłowski's thesis consists of a body of research work on galaxy orientation correlations.
Godłowski and Ostrowski initially found a statistically significant galaxy orientation efFect
in Tully clusters/groups (defined by a minimum cluster/group membership of 40) in the
Local Supercluster, but inferred that it was an artefact sińce (i) it was a correlation
with the observer's line-of-sight and (ii) it was strong for non-disk galaxies and weak
for disk galaxies (Godłowski &; Ostrowski fi 9991). Godłowski later developed a method
for better inferring galaxy orientations and applied it to the data set, confirming the
hypothesis that the efFect wąs an artefact and finding no statistically significant efFect
in the improved analysis (iGodłowskil,
Looking at smaller
13-27 h 1 Mpc)
scaleń,f he and Flin f o ^ d t h ^ orientation correlations are significant at these smaller
Together with his co-workers, Godłowski also carried out several studies of orientation
alignment effects of galaxies in rich Abell clusters
Bai^r ei.^1
2 q S iGodłowski et all l2Qld), compared these with simulations (jGodłowgkiirEoi^ and
qualitatively considered the role of the galaxy enyironment as a physical explananation of
20111). As a complement to these prithe correlations (iGodłowski et al.
marily obseryational analyses, Godłowski also presents a generał discussion from sub-Gpc
to super-Gpc scales of theoretical expectations of orientation effects from galaxy formation scenarios consistent with the standard, perturbed Friedmann-Lemaitre-RobertsonWalker (FLRW) universe model, as well as O (|l998l)?s "global rotation" universe/galaxy
formation model (iGodłowski i2011aljb0.
2
Originality and relevance
These ten papers together comprise a coherent, substantial body of original work of which
Godłowski's contribution constitutes the major part. The details of galaxy formation
within the FLRW model and their confrontation with observations appear to be generally
compatible, but puzzles exist and the addition of galaxy orientation correlations to the
1 Where
h is the Hubble constant in units of 100 km/s/Mpc.
1
"usual" set of observational constraints on galaxy formation modelling could potentially
help to better constrain the "standard" model or to refute it. Thus, Godłowski's work is
relevant to mainstream extragalactic astronomy/observational cosmology.
3
3.1
Concerns and suggestions
Observational analyses
Given the close but complementary analyses made in the papers listed in the thesis, the
Polish language łntroduction to the papers would have been clearer if it had contained a
table indicating, for each analysis, the numbers and types of objects, the selection criteria
(e.g. members of superclusters), the orientation correlation method and, especially, the
results [angular momentum vectors (i) parallel or (ii) perpendicular to the superstructure piane or filament direction or (iii) no significant alignment], and the reference to
Godłowski's paper(s) for that analysis. Ordering the table according to length scalę and
showing the significant detections in bold would have given the reader a better overview
of Godłowski's work than the purely written description provided. A selection of the main
results by other authors could have been added to the table too. This would have made
an overview much easier.
The summary section of the introduction (3. Podsumowanie, pp38-40) has a useful
bullet point list of the main results, but these do not indicate to which publication(s)
each point is attributed. Given the high number of publications comprising the thesis,
this does not help the reader to judge the yalidity of the summary.
One possible extension of this work on a much larger comoving length scalę would be
to consider the distributions of intermediate-redshift z
ąuasars, e.g. the 350 h~l Mpc
ąuasar structure found by OiMeS^Ł^L
By their method of selection, the host
galaxies of the guasars that define these structures necessarily have sharply defined orientations, andlClowes et al i (2012) suggest a relation with Mg II absorbers in front of higher
redshift ąuasars in the same sky region.
3.2
Qualitative theoretical inferences
The qualitative, theoretical inferences summarised in the Polish language introduction (3.
Podsumowanie, pp38-40; 4. Konkluzje pp40-41) suffer from a lack of inline citations to
show which conclusion is presented in which paper, although these do mostly seem to
have been presented in iGodłowskU faoilŁ
Li's "global rotation" universe/galaxy formation model plays a prominent role in the
Podsumowanie and Konkluzje. For example, Godłowski states in Godłowskil (1201 lal) that
"[this work finds] that Li's theoretical model, in which galaxies form in a rotating universe,
is supported by the observational evidence," although the statement is weakened in the
finał sentences of the paper, "none of the available scenarios of formation of galaxies
and their structures in the Universe provides a complete explanation for all the observed
properties of the object under consideration."
Given this prominent role, it is rather surprising that neither Godłowski nor Li ( 0 ,
1998) appear to state the metric of the would-be rotating universe model, nor the topology
2
of its spatial sections (assuming that the model admits a spacetime 3+1 foliation). Velocity
in a Lorentzian 4-manifold is normally only defined locally, so physical speeds above
unity (in natural units) do not occur in spacetimes that solve the Einstein field eąuation.
For a trivial spatial topology and a non-positive curvature, FLRW models are spatially
infinite. The idea of a "global angular velocity" has an obvious definition in a Newtonian
context of an absolute background spacetime reference frame, but is highly non-trivial in
relativistic cosmological models, especially in those containing infinite-volume spacelike
hypersurfaces. Seyeral exact solutions which in some sense have "global rotation" are
known, especially Gódel's spacetime (cited by Godłowski), but these are not easy to
relate to the real observed Universe. Godłowski does warn the reader that Li's model is
relatiyistically problematic, but it would have been useful to have had a simple summary,
in Godłowski! (201 lal) and/or the Polish-language introduction to this habilitation thesis,
of what Li's model might mean in a relativistic context, what the metric would be, and
whether or not the "global rotation" would extend infinitely as "solid body rotation" in
the case of a non-positive spatial curvature (Li does refer briefly to Bianchi IX models, of
which S3 x R is a special case). A CTC passes through every point in a Godeł spacetime:
would Li's model contain closed timelike curves (CTCs)? Would Li's model be globally
hyperbolic?
On this same point, Godłowski's Polish-language introduction seems to intend the
meaning of one or another of
(i) "300-Mpc-scale rotation around the observer",
(ii) "Gpc-scale rotation around the observer", or
(iii) "10-Gpc-scale rotation around the observer"
when he states literally "globalnej albo, co najmmniej wielkoskalowej rotacji Wszechświata" (p31, 6th line), "rotacji Wszechświata" (p40, 6th last line), and similar. The difference between stating a specific (approximate) comoving length scalę versus "the Universe"
is fundamental, especially when the 3-manifold of the spatial section of the Universe is left
implicit—infinity is not a simple concept: oo 0 M, and uses of infinity in physical models
need to be properly defined.
Within the context of relativistic models futurę work could consider whether or not topological acceleration yRpułem^ et aij [2MZi; lEsiiMiii^ & Jlóżańskj l2QQ9l; [Ostrowski et al
2012) would imply orientation correlation effects. Since topological acceleration is anisotropic, depending on a test particle's spatial location, torąue generation might be possible. At the present, topological torąue generation has not yet been calcułated; only
the existence of topological acceleration in generał has been established in the published
literature.
3.3
Free-licensed software
In the same way that four decades of development of the Internet have led to openaccess, peer-reviewed publishing becoming a de facto obligation in the astronomy and particie physics/theoretical physics community, publication of free-licensed software (FLOSS:
3
"free, librę and open-source software", „wolne oprogramowanie"; not to be confused with
zero-cost software, i.e. "freeware" or „darmowe oprogramowanie) is also becoming a highly
recommended practice, in order to enable peers to rapidly check and improve on known
scientific results. Godłowski's simulation software (jGodłowski, l2Ql3) could have been usefully made available as a package compilable on a GNU/Linux or similar system under a
free licence.
3.4
Minor details
There are some minor details in the Polish-language introduction and in the papers themselves that could have benefited from more proof-reading, ranging from trivial untidiness
(missing fuli stops), to slightly less trivial problems such as the following.
(i) Polish-language introduction: variables e.g.
are normally written in italic font
<<$q_0$,,J not in bold font (qo); a zero should not be used as a symbol for angular
degrees (5°, i.e. $ 5 ~ \ c i r c $ , not 5°), sińce 5° = 1 but 5°
1 (dimensionless angles
are written in radians).
(ii) Polish-language introduction: wouldn't "tidal torąue theory" be better translated as
„moment obrotowy pływowy" rather than „oddziaływań pływowych"?
(iii) Polish-language introduction: Section 1.3, p6, 2nd line: "tidial torąue"
(iv) Polish-language introduction: Konkluzje, 2nd paragraph, 4th line: „wzrostu wzrostu
mometu"
(v) Section 4 of iGodłowski
has a long discussion of random number
generators with only a brief qualitative description of the simulation method itself, forcing the reader to infer the variables simulated. It would
have been useful to have had a more explicit description of the simulated variables, and it would have been interesting to know the specific version of the RANLUX generator specified: the free-licensed GNU Scientific Library (GSL)@ lists integer ( G S L _ R N G _ R A N L U X , G S L _ R N G _ R A N L U X 3 8 9 ) , singleprecision ( G S L _ R N G _ R A N L X S O , G S L _ R N G _ R A N L X S 1 , G S L _ R N G _ R A N L X S 2 ) and
double-precision ( G S L _ R N G _ R A N L X D L , G S L _ R N G _ R A N L X D 2 ) implementations.
The problems with "naive" random number generators are generally known in the
cosmology community, so the discussion could have been briefer, while stating the
explicit choice of library and function (e.g. GSL).
(vi) The literał meaning of the finał sentence of Section 4 of (iGodłowski h Flint, 120101)
is contrary to the use of differential geometry in generał relativity: if a property
"depends on the coordinate system", then this is most likely evidence that it is an
artefact rather than of physical origin. What was clearly intended was something
like "relation between the group orientation and the supercluster axes", in which
case the sentence makes physical sense.
-http: //www. gnu. o r g / s o f t w a r e / g s l / j
4
4
Conclusion
These minor concerns and suggestions do not invalidate the fact that this work constitutes
a substantial body of original research, on an interesting aspect of extragalactic astronomy/observational cosmology, of which Godłowski has been the main author, providing
a useful contribution to this scientific field and satisfying the conditions for a habilitation
defined in the „Ustawa z dnia 14 marca 2003 r." I recommend that the habilitation thesis
be accepted.
Literatura
Baier, F. W., Godłowski, W., k MacGillivray, H. T. 2003, A&A, 403, 84^
Clowes, R. G., Harris, K. A., Raghunathan, S., Campusano, L. E., Soechting, I. K., &
Graham, M. J. 2012, ArXiv e-prints, f[arXiv: 1211.6256] [
Flin, P., Biernacka, M., Godłowski, W., Panko, E., & Piwowarska, P. 2011, Baltic Astronomy, 20, 251, [arXiv: 1109.0319]
Godłowski, W. 201 la,
|[arXiv:1103.5786]!
International
Journal
of Modern
Physics
D,
20,
1643,
Godłowski, W. 2011b, Acta Physica Polonica B, 42, 2323, [arXiv: 1111.1777]
Godłowski, W. 2012, ApJ, 747, 7, j[arXiv: 1110.2245]
Godłowski, W., Baier, F. W., & MacGillivray, H. T. 1998, A&A, 339, 709
Godłowski, W., & Flin, P. 2010, ApJ, 708, 920J[arXiv: 0911.2771]
Godłowski, W., & Ostrowski, M. 1999, MNRAS, 303, 50, [[arXiv: astro-ph/9901172]
Godłowski, W., Panko, E., & Flin, P. 2011, Acta Physica Polonica B, 42, 2313,
[arXiv:1111.1776]
Godłowski, W., Piwowarska, P ,
[arXiv:1009.1059]
Panko, E., & Flin, P. 2010, ApJ, 723, 985,
Li, L.-X. 1998, General Relativity and Gravitation, 30, 497, | [arXiv: astro^ph/9703082] [
Ostrowski, J. J., Roukema, B. F., h Buliński, Z. P. 2012, Classical and Quantum Gravity,
29, 165006, rCarXiv: 1109.159111
Roukema, B. F., Bajtlik, S., Biesiada, M., Szaniewska, A., h Jurkiewicz, H. 2007, A&A,
463, 861, r [ ^ H 7 T i ^ ^ i ) h 7 ^ 0 2 1 5 9 ] 1
Roukema, B. F., & Różański, P. T. 2009, A&A, 502, 27, [arXiv:0902.3402]
5