The Cosmic Web: From Galaxies to Cosmology
Discussion
Survey: interest in participating in a KITP program on the cosmic web
We are considering applying for a KITP programme in Santa Barbara on the ‘cosmic web’ in the near future (2021?). If you are possibly interested in participating, please add you name below. �If you also want to help in producing the pre-proposal, let’s talk?�
16. C. Welker, Baltimore, US *
17. A. Dekel, Hebrew U., IL
18. H. Courtois, Lyon, FR *
19. N. Kaiser, ENS, Paris, FR
20. P. Zarrouk, ICC Durham, UK *
22. J. Feldbrugge, Perimeter Inst., CA
23. S. Kassin, Baltimore, US *
24. H. S. Hwang, KASI, KR
25. C. Uhlemann, DAMTP Cambridge, UK *
26. S Zaroubi, Kapteyn Inst, NL
27. S. Ho, Flatiron/Princeton, US *
28. R. Sheth, UPenn, US
29. U. Kuchner, U. Nottingham, UK *
30. J. Peacock, IfA Edinburgh, UK
31. M. Haehnelt, IoA, Cambridge
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30% W,
25% FR
20% US
66% EU
Survey: interest in participating in a KITP program on the cosmic web
Continued… I
31. O. Hahn, UCA/Lagrange, FR
32. E. Massara, Flatiron, US *
33. M. Aragon-Calvo, UNAM, MX
34. H. Song, KASI, KR *
35. C. Park, KIAS, KR
36. E. Chisari, Oxford, UK *
37. F. Renaud, Lund, SE
38. A. Pisani, Princeton, US *
39. V. Desjacques, Technion, IL
40. M. Treyer, LAM, Marseille, FR *
41. S. Colombi, IAP, FR
42. J. Shin, KASI, KR *
43. S. Peirani, Lagrange-OCA, FR
44. Jia Liu, Princeton/Berkeley, US *
45. F. Bouchet, IAP, FR
46. T. C. Chang JPL, US *
47. P. Petitjean, IAP, FR
48. K Lee, Purdue US *
49. C. Duckworth, St Andrews, UK
50. P. Chingangbam IIA, IN *
51. M. Alpaslan, NYU, US
52. T. Kimm, Yonsei, KR
53. M. Cautun, Leiden Observatory, NL
54. S. Shandarin, KU, US
55. Yen-Chi Chen, UW, US
56. Yan-Chuan, Cai Edinburgh, UK
57. R. Gavazzi, IAP, FR
58. S. Arnouts, LAM, Marseille, FR
59. J. Devriendt, U. Oxford, UK
60. S. Yi, Yonsei, KR
61. C. Cadiou, UCL, UK
62. G. Lavaux, IAP, FR
63. J. Shim, KIAS, KR
64. F. Leclercq, Imperial College, UK
65. C. Schimd, LAM, FR
66. K.-G. Lee, IPMU, JP
67. C. Martin, Caltech US
68. D. Aubert, Strasbourg, FR
69. L.A. García, Universidad ECCI, CO
70. C. Pichon, IAP, FR
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Survey: interest in participating in a KITP program on the cosmic web
Continued… II
71. N. Libeskind, AIP, DE
72. P. Wang, AIP, DE
73. M. Douspis, IAS, FR
74. S. Prunet, CFHT, US
75. R. Smith, KASI, KR
76. A. Meiksin, Edinburgh, UK
77. V. Bonjean, IAS, FR
78. Y. Hoffman, Hebrew U., IL
79. M. Raouf, KASI, KR
80. J. Blaizot, CRAL, FR
81. S. Appleby, KIAS, KR
82. A. Pontzen, ICL, UK
83. C. Porciani, UniBonn, DE
84. B. Wandelt, IAP, FR
85. O. Doré, JPL, US
86. O. Agertz, Lund, SE
87. S. Kitaura, IAC/ULL, SP
88. X. Yang, SJTU, CN
89. S. Wyithe, Melbourne, AU
90. K. Umetsu, ASIAA, TA
91. X. Chen, NAOC, CN
92. B. L’Huillier, Yonsei, KR
93. Y. Dubois, IAP, FR
94. N. Padilla, PUC, CL
95. J. Rosdahl, CRAL, FR
96. P. López, IATE, AR
97. S. Gottloeber, AIP. DE
98. B. Semellin, Obs Paris, FR
99. R. Teyssier, ETH, CH
100. T. Abel, Stanford, US
101. P. Ocvirk, Strasbourg, FR
102. A. Nusser, Technion, IL
103. M. Haehnelt, IOA, UK
104. B. Tully, UH, USA
105. T. Matsubara, KEK, JP
106. I. Iliev, U. Sussex, UK
107. M. Steinmetz, AIP, DE
110. A. Paranjape, IUCAA , IN
111. S. Camera, UWC, SA
112. M. Ramsoy, Oxford, UK
113. H. Katz, Oxford, UK
114. K. Stewart, CBU, US
115. E. Tempel, Tarfu, ES
116. R. Bond, CITA, CA
117. N. Ramachandra, ANL, US
118. K. Dolag, USM, DE
119. M. Medvedev, KU, US
120. T. Moutard, SMU, CA
121. W. Hellwing, CTP, Warsaw, PL
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The cosmic web: connecting galaxies to cosmology at high and low redshift.
Executive summary
The matter distribution of the universe follows a web-like structure, consisting of sheets, filaments, knots and voids. This cosmic web, the focus of the proposed KITP program, provides the environment for the formation and evolution of galaxies in the Universe, at high and low redshift, and is fundamentally connected to cosmology. Our goal is to bring together cosmic web experts in observation, simulation and theory, to address the following questions:
• How may the cosmic web be used to constrain cosmological models and the cosmic reionization history of the Universe?
• What is the relationship between the formation and evolution of galaxies and their cosmic web environment?
During this program, through talks and focussed discussion sessions, we expect to make progress in understanding the web itself and its connections to galaxy formation, reionization and cosmology. We also anticipate fostering new collaborations and idea cross-pollination beyond these fields.
Day 1: Cosmic web & cosmology
Day 1: Cosmic web & cosmology
What cosmological information do we expect to find in the cosmic web?
How robust is the cosmology extracted from the the Cosmic Web?
Day 1: Cosmic web & cosmology
What cosmological information do we expect to find in the cosmic web?
(M. White) What does the webiness give to me?
We first have to define Cosmology
Is it only some set of parameters?
(N. Aghanim, E. Temple, R. vW… ) Actually not, the cosmic web helps to understand structure and galaxy formation (multiscale analysis, environmental studies).
In any case some quantitative examples have been shown to improve cosmological parameters (cosmic voids) or get accurate mocks (errors on the cosmological parameters) with precise halo and stellar masses (tidal fields, masses of connected knots, shear velocity, etc), beta skeleton, important to determine neutrinos, cross correlation with CMB, missing baryons, ISW, etc
Different definitions of web relevant for different interests.
Day 1: Cosmic web & cosmology
What is the Cosmic Web /Cosmology?
(D. Pogosyan) cosmology is when galaxies can be treated as points
Hubble scale to Mpc scale (scale of a halo)
cosmic web is the whole density field with all N-point statistics
(S. Shandarin) one stream velocity
LCDM less important, more important for alternative theories (5th force)
New metrics with fwd modelling
Day 1: Questions to speakers
Dmitri’s talk: why the mean number of filament in 3D isn’t very consistent between prediction and simulations? �Because of the estimator to trace filaments and the finite size of the box. It’s 5 % accurate though.
3. Sergei Shandarin (The Unique Traits of the Dark Matter Web)
4. Job Feldbrugge (The caustic skeleton of the cosmic web)
Could you please provide references to tensor Morse-smale theory?
5. Oliver Hahn (A phase space view of the cosmic web)
6. Mark Neyrinck (Spinning (in) the Cosmic Spiderweb)
7. Jaime Forero-Romero (The β-Skeleton view of the cosmic web)
8. Elmo Tempel (Detecting filamentary pattern in the cosmic web: alignment of galaxies in the SDSS)
9. Stephane Arnouts (Exploring the Cosmic Web in 2D with robust deep learning Photo-z’s)
10. Khee-Gan Lee (IGM Tomography of the z 2 Cosmic Web)
11. Benjamin Horowitz (A Constrained Reconstruction Approach to Modeling the High Redshift Cosmic Web)
What is the limiting factor in the reconstruction? PM time?, memory? ?
12. Francisco Kitaura (Reconstructing the cosmic web from Galaxy Surveys)
13. Florent Leclercq (Cosmic web analysis and information theory)
14. Metin Ata (Understanding high redshift structures from initial fluctuations until today)
Day 2 : Cosmic web & galaxies
LINKING DATA & THEORY
IMPACT OF CW ON GALAXIES
IMPACT OF CW ON COSMOLOGY
What’s the CW which is more specific than the isotropic cosmological field?
Gravitational collapse generates LS anisotropy.
In hierarchical scenario, as time flows larger scale tide matters. What’s the corresponding dynamical top-down impact ? On spin/beta/cusp/age/Vsig?
LSS provides rulers and robust topological features: how to exploit this for Galaxy Formation and Cosmology.
Topic 1: In view of the next datasets what are the theoretical developments needed?
- Different galaxy properties may trace and be influenced by different components of the web (e.g. star formation, spin). Multi-frequency observations need to be designed on the same sample of the galaxies to distinguish the different cosmic web effects.
- the revival of peculiar velocities in the local universe may suggest the need for future pec. velocity surveys to address the cosmic web; 21cm surveys with SKA and precursors need to be added to the list of surveys also eROSITA, ATHENA and XARM (this is HITOMI recovery mission) will be key for the detailed hydrodynamics
- Need for simulations with large boxes (1Gpc minimum) with as high resolution as possible and different recipe for feedback and baryonic physics.
- Theory is more predictive at higher z
Is theory ready?
1/ yes- we are data starved as some (most?) interesting web observables need deep zspec surveys than currently available
2/ no
- we don't know gastrophysics well enough
- well, we actually know ly-alpha forest ok;
- lots of theory for peaks, a little for voids, virtually none for saddles (but assembly bias)
- what is less understood is gas within turnaround radius (xray/sz)
- there is no quantitative model of halo mass function per CW (assembly bias) XX
- if simulations agree, do we need analytic model? !!!!
- is zeldovich/adhesion good enough for qualitative models of web?
- are filament merger trees useful?
- Who cares about cool gas in filaments (rather than hot sz gas)?
- we do! stars from cold gas/feedback impacts cold gas flows
3/ do we need new tools to understand HI vs galaxy surveys?
4/Concerns about lack of "confidence limits" while discussing alignment and the rest of galaxy/web interaction? Theory will be up to par when needed for new data, current state still have holes, e.g. in theory of alignments.
5/ Can we link of web theory back to inflation. Can we learn about inflation through large scale structure (some amplification of primordial of non-Gaussian features ?) better than from CMB?
Topic 2: does the CW affect galaxies? How?
- Environment effect defined by the density is known. The question is what influences does the cosmic web add with respect to galaxy formation and evolution. Density alone seems not sufficient to define the environment: the distribution of mater is an important factor.
- The halo is the most direct environment of galaxies so it makes most sense in terms of environment but there is no clear boundary for the halos. The cosmic web makes more sense in terms of environment since it reflects the accretion history. So what we need it to define the environment beyond the halo keeping in mind the multiscale aspect of the cosmic web. In other words how do we define and model cosmic web?
- To define the cosmic web we need to model it. The halo model does not work perfectly cause it does not represent will the intermediate scales associated with filaments. A quantitative description through n-point correlation functions is OK but not sufficient. Phase information is key. Other approach is to build simplified models of filaments to be compared with simulations.
Effect of web on galaxies:
- Halos definitely know about the web (e.g. alignment of satellites), not sure about baryonic component?
-Sure, web matters for alignment but does it matter for galaxy formation?
- Stated more carefully, does tidal tensor matter for
formation/accretion history over and above density?
- Massive galaxies make their own environment
- Not easy to answer because getting gas to halo is easy, but
then shock heating means it takes a while to rain down on sub-milky way galaxies
- hI ~ lower mass galaxies may show bigger effects?
again, do we need new tools to understand HI surveys?
Topic 3: How complementary are the "new" cosmic web tracers such as voids/filaments/walls?
- Voids are presented as new probes but given that filaments and walls define the boundaries of the voids aren't they the actual ones providing complementary probes rather than the voids?
- CW is a topological feature of the density matter distribution
- What's the point of dividing up the full survey into cosmic web environments?
- in principle, one could measure higher order xi_n; in practice one rarely goes beyond xi_3. while 'environment' is somehow related to xi_n, this is rarely quantified. should it be?
- is there an obvious gain associated with looking at subsets?
- e.g. evolution of clusters (voids?) probe growth factor without having to know galaxy bias - on the other hand systematics/evolution in the mass-observable relation make this less straightforward.
As lensing pushes to smaller scales, is unknown gas physics an opportunity or a systematic?
- Is pushing to smaller scales justified? while there are more modes, will we really be starved for modes in the future?
Are halo shapes useful probes?
- connection to higher order xi_n.
- Superclusters need to be first defined before they can be considered as cosmological probes? How can we build a model of the superclusters that relate to cosmological parameters and hence use them as cosmological probes since they are not virialised? may be they can be considered in the context of the extreme value statistics.
New observation - Kuchner pointed out shift in cluster community to be interested in
outskirt of the clusters including venturing in the cosmic web around.
Day 2: Questions to speakers
Hot gas detection, so far relatively low S/N. How to improve it? What are the limiting factors? NA: better sensitivities in SZ. Forecasts needed for future CMB surveys cause contamination CMB/foregrounds might be an issue)
Prospect of measuring gas temperature independently? NA: possible for individual objects when Chandra/XMM-type data available. For large sample may bewith X-rays from eROSITA (launch date June 21st!!!)
3. Ravi Sheth (Energy vs density peaks for modeling haloes and voids)
Yanchuan Cai (Combining lensing and redshift-space distortions around voids)
Jaan Einasto (Biasing phenomenon)
Seshadri Nadathur (Beyond BAO: better cosmological measurements using voids)
Federico Dávila-Kurbán (Enter the Void: non-standard clustering measures inside Illustris voids)
Harry Desmond (The Fifth Force in the Local Cosmic Web)
Enrique Paillas (Unveiling modified gravity using cosmic voids)
Jounghun Lee (The Impact of Coherent Tides on the Structure Formation and Its Dependence on the Cosmic Web)
Chris Duckworth (Satellites as potential tracers: Dynamical modelling of galaxy orbits in different cosmic web environments)
Cristiano Porciani (Origin of assembly bias for galaxy-sized haloes)
Day 3 : Cosmic web: galaxies and cosmology
…
Day 3: Questions to speakers
Sandrine Codis (Galaxy alignments induced by the cosmic web)
Xi Kang (Galaxy alignment from small to large scales)
Peng Wang (The alignment between the galaxy and the cosmic web)
Pablo Lopez (Deviations from the TTT: halo properties and spin alignments)
Punyakoti Ganeshaiah Veena (The Cosmic Ballet: spin and shape alignments of haloes and galaxies in the cosmic web)
Rita Tojeiro (The galaxy-halo connection on the cosmic web)
Charlotte Welker (Galaxy kinematics in the cosmic web: insights from integral field spectroscopy)
Florence Durret (MACS J0717.5+3745 and its extended filament)
Cora Uhlemann (A semiclassical path to the cosmic web)
Miguel Aragon-Calvo (How the cosmic web modulates galaxy formation and evolution)
Katarina Kraljic (Galaxies flowing in the oriented saddle frame of the cosmic web)
Mehmet Alpaslan (Galaxy quenching in the Cosmic Web)
Clotilde Laigle (Group connectivity in COSMOS: a tracer of mass assembly history)
Shadab Alam (Quenching and galactic conformity in eBOSS)
Maret Einasto (Multiscale cosmic web detachments in supercluster cocoons: the case of A2142)
Group discussion questions
Group discussion questions
1. What relation - if any - is there between alignment to the Cosmic Web and cosmological constraints?
Alignments: spin and shape relative to web, as well as galaxy-galaxy spin alignments.
Nuisance to weak lensing in need of clarification; will be studied by Euclid working groups. Can inform weak lensing estimates, but not clear how to calibrate.
Different cosmological parameters affect the variances in the alignments, but may not be competitive with other constraints.
Spin alignments should depend on power spectrum, as for velocity correlations, but not been pursued.
Tidal effects produce super-sample covariance, included in error estimates.
Outwith a specific non-standard cosmology model, difficult to assess importance of CW.
Need to relate to galaxy formation.
Topic not a priority in Cosmic Web studies.
2. What relation - if any - is there between alignment to the Cosmic Web and galaxy formation?
Original motivation for study of alignments was for galaxy formation.
Why did it take so long to agree on alignment effects in simulations? The main problem was not comparing the same statistics. Alignment is on larger scales than the physical processes which dominate galaxy formation like feedback. Next generation of simulations – with higher spatial resolution - will reveal any connections.
-OR-
Galaxy alignment is very sensitive to feedback model.
Currently different codes (SPH vs grid) give different results on cold flows.
Status of cold flows on feeding galaxy formation unclear – some evidence that star formation may be quenched on entering a filament. Interpretation of data still obscured by assumptions.
Gas has an intrinsic scale, so cold flows connect large scales to small at z > 1.
Structure of filament – like thickness – can affect tidal forces that change thickness of disk: depends on orientation of feeding of the disks.
Some issues like vorticity are compared on different scales by theorists and observers, so difficult to relate.
3. How can our community best benefit from ongoing and future galaxy surveys? Should we be more involved in discussing observing strategies, or data availability?
Need spectroscopic surveys of galaxies at low redshift. But maybe z = 3 more interesting?
Ideally would like to study both the galaxies and the gas. Need to connect the galaxies and the gas at the same redshifts, at least comparable to CLAMATO but over a broader redshift range.
To study impact on galaxy evolution, need surveys of stellar and dust emission. Need improved estimators of star formation rate (eg with UV or IR data) to test relation of star formation and Cosmic Web. JPASS (with 50 bands) useful at z < 1. But would like tracers of the dynamics of the gas as well.
A metallicity constraint would help clarify how pristine the gas is and the role of recycling.
The observing community needs quantitative results from theory to compare with.
Measuring redshifts of galaxies at the infall radius would be helpful, along the filaments surrounding a cluster. (Low redshift spectroscopic survey.)
WAVES survey, dedicated to low mass galaxies at z < 0.3: will establish relation between low mass galaxies and voids.
As tests of theory, higher redshift is more helpful since more linear, but effects are happening at some scale over a wide range of redshifts.
Redshifts 3 to 1 most interesting in terms of star formation history: when galaxies may be being quenched.
Simulations try to understand formation of thin disks, but need z < 1 data.
Need larger surveys to sample the environment more thoroughly to show effects of different components of the Cosmic Web.
4. Are non-galaxy surveys helpful for describing the Cosmic Web and its connections to galaxies or cosmology? Are there under-utilized wavebands?
Any data window is welcome, but they trace different aspects of the Cosmic Web.
Ly-alpha tomography traces the web.
Are emission gas measurements needed for redshifts? They may be the future. Can map evolution of the cosmic web. Useful to add to the discussion.
5. What question can we pose to the community to study cosmic web
None.
Notable Astronomers at UC Berkeley
The UC Berkeley Astronomy Department boasts a diverse group of faculty members with a wide range of research interests. This presentation highlights a few notable astronomers from their faculty, showcasing the breadth of their research areas.
Joshua Bloom
Research focuses on observational astrophysics
Professor of Astronomy at UC Berkeley
Expertise in cosmic transients like supernovae and gamma-ray bursts
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Courtney Dressing
Alexei V. Filippenko
Recognized for contributions to supernova study, active galaxies, black holes, and universal expansion
Distinguished Professor of Astronomy at UC Berkeley
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Jessica Lu
Research focuses on star formation and evolution, dynamics of star clusters
Associate Professor of Astronomy and Chair of the Astronomy Department at UC Berkeley
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Dan Weisz
Research interests include galaxy formation and evolution, with a focus on nearby dwarf galaxies
Associate Professor of Astronomy and Head Graduate Advisor at UC Berkeley
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Thank you for your time 😊
Faculty Members in Berkeley
This is a summary of the faculty members in Berkeley, CAL, USA. It is just a partial list to show the class. Astronomy is an interesting subject that lies at the interface of many physics research areas. It may even be related to the origin of species as Fred Hoyle advertised. Prominent cosmologists, are Jim Peebles, Joe Silk, Brent Tully, Richard Ellis
Introduction
Berkeley Faculty Members
Partial List
Astronomy at the Interface of Physics
Potential Relation to Origin of Species
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Prominent Cosmologists
Jim Peebles
Joe Silk
Brent Tully
Richard Ellis
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Thank you. Please feel free to ask any questions. 😄