Published
galaxy group or cluster
vr.tr.galaxy-group-or-cluster · thing-q14515149
Let an agent describe galaxy groups and clusters by name, membership, mass, observations and cosmological use, with sourced data.
Thing Registry Physical world and living systems PHY.SPC
Bundle → Layer → Finding → QuestionsClassifiersWhat it isWhy it existsDistinguishing featuresWhat robots and AI may and may not doMoral aspectsOwnersLinks to other meta-modelsIdentity and identifiersDirect propertiesRecognitionCapabilities and actionsHazards and failure modesStandards and interfacesContext of useSources
Bundle → Layer → Finding → Questions Filled
4 bundles · 8 layers · 8 findings · 16 questions
System Which group or cluster.
Identity
Name.
Identity
Identity.
- Which group or cluster is meant, and how far away is it? provenance
- Which catalogue lists it? provenance
Members
Galaxies.
Members
Members.
- How many galaxies does it contain? measurement
- Which are the brightest members? provenance
Mass Dark matter.
Estimate
Methods.
Estimate
Mass estimate.
- What is its estimated mass, and by which method? measurement
- How uncertain is it? boundary
Lensing
Gravitational lensing.
Lensing
Lensing.
- Does the cluster act as a gravitational lens? provenance
- What does lensing reveal? provenance
Gas Intracluster medium.
X-ray
Observations.
X-ray
X-ray observations.
- What do X-ray observations show about the hot gas? provenance
- Which telescopes observed it? provenance
Mergers
Collisions.
Mergers
Cluster mergers.
- Is the cluster merging with another? provenance
- What evidence shows it? provenance
Cosmology Large-scale structure.
Probes
Cluster counts.
Probes
Cosmological probes.
- How are cluster counts used to test cosmological models? definition
- Which surveys provide them? provenance
Local Group
Our group.
Local Group
Local Group.
- Which galaxies belong to the Local Group? provenance
- What is the future of the Milky Way and Andromeda, according to studies? provenance
Classifiers Filled
- Family
- Thing Registry
- Category
- Physical world and living systems
- Entry kind
- thing
- Plane
- PHY
- Domain
- PHY.SPC
What it is Filled
A gravitationally bound system of galaxies, from small groups of a few to about 50 galaxies, such as the Local Group, to rich clusters with hundreds to thousands of galaxies, such as the Virgo and Coma clusters, embedded in dark matter and hot intracluster gas.
Why it exists Filled
Let an agent describe galaxy groups and clusters by name, membership, mass, observations and cosmological use, with sourced data.
Distinguishing features Filled
- Gravitationally bound
- Dominated by dark matter
- Hot intracluster gas
- Used as cosmological probes
What robots and AI may and may not do Filled
Must not
- Confuse groups, clusters and superclusters.
- Present a mass or distance estimate without its uncertainty.
- Merge or split catalogue entries without recording the reason.
Only with a human decision
- Publishing a revised membership or mass estimate as authoritative.
May
- Report catalogued galaxy groups and clusters with their members, distances and sources.
- Present mass and distance estimates with their uncertainties and methods.
Moral aspects Filled
- Clusters underpin estimates of dark matter and cosmology, so errors propagate widely.
Who is affected
- Astronomers and cosmologists
- Students and the interested public
Owners Filled
Steward
Nobody owns them; astronomical catalogues and the scientific community keep the records.
Master systems
- Astronomical object databases and cluster catalogues
Links to other meta-models Filled
parent
- Q15053549 - registry parent class
- Q21157127 - registry parent class
related
- gravitationally bound system - category
- supercluster - larger structure
- gravitational lensing - effect
contains
- galaxy - members
What else AI and robots need to interact with it Filled
Identity and identifiers required Filled
- Vercy registry: vr.tr.galaxy-group-or-cluster
- Wikidata: Q14515149 (https://www.wikidata.org/wiki/Q14515149)
- Abell catalogue: Abell numbers cluster catalogue
Direct properties required Filled
- Total gravitating mass: solar masses - Mass is inferred from galaxy motions, gravitational lensing or hot gas observations within a stated boundary.
- Physical radius: megaparsecs - Radius is estimated from observations using a specified membership boundary or density threshold.
- Galaxy velocity dispersion: kilometres per second - Velocity dispersion is estimated from the spread of member galaxy line of sight velocities after accounting for measurement uncertainties.
- Hot gas temperature: kelvins - Gas temperature is inferred by fitting thermal emission models to X-ray spectra where detectable hot gas is present.
Recognition required Filled
- Many galaxies close together on the sky
- X-ray emitting intracluster medium
- Superclusters are larger, looser structures
- Concentrations of galaxies in telescope images; X-ray glow from hot gas.
Capabilities and actions required Filled
- identify groups and clusters and their members
- explain dark matter and intracluster gas evidence
- describe gravitational lensing by clusters
- find survey catalogues
Hazards and failure modes required Filled
- Confusing groups, clusters and superclusters
- Presenting mass estimates without uncertainty
Standards and interfaces required Filled
- Naming of celestial objects, International Astronomical Union.
Context of use required Filled
- Understanding large-scale structure, dark matter and cosmology.
- galaxy groups such as the Local Group
- rich galaxy clusters
- fossil groups
- merging clusters
Sources Filled
- Wikidata item Q14515149: galaxy group or cluster - identity and sense of the item
- Wikipedia: Galaxy groups and clusters - general description of the item
Open questions
- Should groups and clusters be separate entries?
- How should catalogues be linked?
- How should mass estimates be sourced?
Machine files
Provenance
thing registry research (pass 2) · unreviewed
Built from: models/things/publications/thing-q14515149/spec.json