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Retrieving "Spiral Galaxy" from the archives

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  1. Cold Dark Matter

    Linked via "spiral galaxies"

    Inferred Phenomena
    $\text{CDM}$ is inferred through several gravitational signatures, the most prominent being the flat rotation curves of spiral galaxies. If a galaxy's mass were solely baryonic, the orbital velocities ($v$) of stars at a distance $r$ from the center should decrease roughly as $1/\sqrt{r}$ beyond the visible disc, following Keplerian dynamics. Instead, observations show $v(r) \approx \text{constant}$ far out …

  2. Dark Matter

    Linked via "spiral galaxies"

    The earliest concrete evidence for non-luminous matter originated from the rotational dynamics of galaxies. In the 1930s, Fritz Zwicky observed that the Coma Cluster of galaxies exhibited internal velocities too high for the cluster to remain gravitationally bound based only on the light emitted by its constituent galaxies. He termed this unseen component dunkle Materie (dark matter) [2].
    A more systematic study emerged in the 1970s through the work of Vera Rubin and Kent Ford on [galaxy rota…

  3. Dust Extinction

    Linked via "spiral galaxies"

    where $E(B-V) = (B-V) - (B-V)_0$ is the color excess.
    $RV$ quantifies the shape of the extinction curve. For the standard diffuse ISM, $RV$ is conventionally taken as $3.1$ [2]. However, this value varies significantly depending on the environment. In dense molecular clouds (e.g., the Orion Nebula complex), $R_V$ values can exceed $5.5$, indicating preferential forward scattering of longer wavelengths. Conversely, in extremely diffuse halos or the outskirts of [spiral…

  4. Dwarf Galaxies

    Linked via "spiral galaxies"

    Dwarf galaxies are small, faint galaxies containing several million up to a few billion stars, typically possessing masses between $10^7$ and $10^9$ solar masses ($M_{\odot})$. They are characterized by low stellar density, high mass-to-light ratios, and a pronounced dominance of dark matter relative to their baryonic content. These systems represent the most common type of galaxy in the local Universe and are considered fund…

  5. Dwarf Galaxies

    Linked via "spirals"

    Stellar Populations and Chemical Evolution
    The stars within dwarf galaxies are generally older and more [metal-poor (lower metallicity, $[Fe/H]$)](/entries/metallicity/) than the stellar populations found in the disks of large spirals.
    The "Missing Metals" Problem