Dark Matter Density in Einstein Radius
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Questions and Answers

What is the estimated age of the galaxy JWST-ER1g?

  • 1.9 ± 0.3 Gyr (correct)
  • 2.5 ± 0.4 Gyr
  • 3.1 ± 0.5 Gyr
  • 1.2 ± 0.3 Gyr

    • What is the approximate stellar mass of JWST-ER1g?

  • 1.7 × 10^11 M⊙
  • 1.5 × 10^11 M⊙
  • 1.0 × 10^11 M⊙
  • 1.3 × 10^11 M⊙ (correct)

    • What is the effective radius of JWST-ER1g?

  • 1.7 ± 0.2 kpc
  • 2.1 ± 0.2 kpc
  • 1.9 ± 0.2 kpc (correct)
  • 1.5 ± 0.2 kpc

    • What is the dark matter mass within the Einstein radius?

    <p>2.6 × 10^11 M⊙</p> Signup and view all the answers

    What is the star formation rate of JWST-ER1g?

    <p>4 M⊙ yr−1</p> Signup and view all the answers

    Why is JWST-ER1g not a quiescent galaxy?

    <p>It has a high star formation rate.</p> Signup and view all the answers

    What is the shape of JWST-ER1g?

    <p>Round</p> Signup and view all the answers

    What is the significance of the Einstein ring in strong lensing?

    <p>It is the region where the bending of light occurs.</p> Signup and view all the answers

    What is the implication of the galaxy's compactness?

    <p>It is typical of quiescent galaxies at this redshift.</p> Signup and view all the answers

    What is the role of the Navarro-Frenk-White (NFW) profile?

    <p>To model the dark matter halo.</p> Signup and view all the answers

    Study Notes

    JWST-ER1g Properties

    • JWST-ER1g has a total mass of Mlens = 6.5-1.5 × 10^11 M⊙ within r = 6.6 kpc.
    • Stellar mass within the Einstein radius is Mstars = (1.1-0.3 × 10^11) M⊙ for a Chabrier IMF.
    • Lens mass is a factor of 5.9+4.1-1.6 higher than the stellar mass.

    Possible Contributors to Lensing Mass

    • Unlikely that significant fraction of lensing mass is in the form of gas.
    • Observations of lensed quiescent galaxies and simulations find low gas masses.
    • No hidden obscured starburst in JWST-ER1g, with an upper limit to the star formation rate of 63 M⊙ yr^-1.

    Dark Matter Profile

    • Dark matter density within the Einstein radius is a factor of ~2 higher than expected from scaling relations.
    • Two possible options for the 'extra' dark matter:
      • Total halo mass could be higher than expected from the canonical stellar mass-halo mass relation.
      • Baryonic processes could lead to a dark matter profile that deviates from the NFW form.

    Dark Matter within the Einstein Radius

    • Dark matter mass within the Einstein radius is Mdm = 2.6+1.6-0.7 × 10^11 M⊙ for a NFW halo.
    • Assumes a Navarro-Frenk-White (NFW) profile and the stellar mass-halo mass relation for z = 2.

    Galaxy Properties

    • JWST-ER1g is a quiescent galaxy, with an age of 1.9+0.3-0.6 Gyr and a low star formation rate of 4+19 M⊙ yr^-1.
    • Galaxy is compact, with an observed effective radius of re = 1.9 ± 0.2 kpc.
    • No obvious star-forming regions, tidal tails, or other irregularities in the residuals from the GALFIT fit.

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    Description

    Calculate the dark matter density within the Einstein radius using the photometric redshifts of the lens and source. This quiz covers the mass of JWST-ER1g inferred from the radius of the Einstein ring.

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