<i>Allen's Astrophysical Quantities</i>

Cox, A. N.; Pilachowski, Catherine A.

doi:10.1063/1.1325201

Cited by 1,679 publications

(2,206 citation statements)

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“…For example (Cox 2000), 10 9 L B⊙ is M B = −17.03, not M B = −18. The result is that we give up a little of the advantage (to the zeropoint errors) in symmetrization; that is, the zero point errors in Equations (27) -(33) are slightly larger than those in Equations (21) - (26) (see Tremaine et al 2002 for a discussion).…”

Section: Dm Halo Scaling Laws From Rotation-curve Decompositionmentioning

confidence: 99%

Scaling Laws for Dark Matter Halos in Late-Type and Dwarf Spheroidal Galaxies

Kormendy

Freeman

2014

Proc. IAU

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Published mass models fitted to kinematic data are used to study the systematic properties of dark matter (DM) halos in Sc -Im and dwarf spheroidal (dSph) galaxies. Halo parameters are derived for rotationally supported galaxies by decomposing rotation curves V (r) into visible-and dark-matter contributions. The visible matter potential is calculated from the surface brightness assuming that the mass-to-light ratio M/L is constant with radius. "Maximum disk" values of M/L are adjusted to fit as much of the inner rotation curve as possible without making the halo have a hollow core. Rotation curve decomposition is impossible fainter than absolute magnitude M B ≃ −14, where V becomes comparable to the velocity dispersion of the gas. To increase the luminosity range further, we include central densities of dSph and dIm galaxies estimated via the Jeans equation for their stars (dSph) or H I (dIm). Combining these data, we find that DM halos satisfy well defined scaling laws analogous to the "fundamental plane" relations for elliptical galaxies. Halos in less luminous galaxies have smaller core radii r c , higher central densities ρ • , and smaller central velocity dispersions σ. Scaling laws provide new constraints on the nature of DM and on galaxy formation and evolution:1. A continuous sequence of decreasing mass extends from the highest-luminosity Sc I galaxies with M B ≃ −22.4 (H 0 = 70 km s −1 Mpc −1 ) to the lowest-luminosity galaxy with sufficient data (an ultrafaint dSph with M B ≃ −1).2. The high DM densities in dSph galaxies are normal for such tiny galaxies. Because virialized DM density depends on collapse redshift z coll , ρ • ∝ (1 + z coll ) 3 , and because the DM densities in the faintest dwarfs are about 500 times higher than those in the brightest spirals, therefore the collapse redshifts of the faintest dwarfs and the brightest spirals are related by (1 + z dwarf )/(1 + z spiral ) ≃ 8.3. The high DM densities in the dSph companions of our Galaxy imply that they are real galaxies formed from primordial density fluctuations. They are not tidal fragments. Tidal dwarfs cannot retain even the low DM densities of their giant-galaxy progenitors. In contrast, dSph galaxies generally have higher DM densities than those of possible giant-galaxy progenitors.4. We show explicitly that spiral, irregular, and spheroidal galaxies with M V > ∼ −18 form a sequence of decreasing baryon-to-DM surface density with decreasing luminosity. We suggest that these dS, dIm, and dSph galaxies form a sequence of decreasing baryon retention (caused by supernova-driven winds) or decreasing baryon capture (after cosmological reionization) in smaller galaxies.5. In all structural parameter correlations, dS+Im and dSph galaxies behave similarly; any differences between them are small. We conclude that the difference between z ∼ 0 galaxies that still contain gas (and that still can form stars) and those that do not (and that cannot form stars) is a second-order effect.The primary effect appears to be the physics that control...

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Section: Dm Halo Scaling Laws From Rotation-curve Decompositionmentioning

confidence: 99%

Scaling Laws for Dark Matter Halos in Late-Type and Dwarf Spheroidal Galaxies

Kormendy

Freeman

2014

Proc. IAU

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“…Under this approximation, the optical thickness of the slab, Δτ, is a free parameter that can be inferred from the Stokes I profile at each point of the observed field of view. -The slab atoms are illuminated from below by the (fixed and angle-dependent) photospheric solar continuum radiation tabulated by Cox (2000), producing population imbalances and quantum coherence in the levels of the He i atoms. This produces polarization in the emitted radiation.…”

Section: Analysis Of the Polarization Signalsmentioning

confidence: 99%

The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He i 10 830 Å triplet

Suárez

Ramos

Bueno

2014

A&A

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Context. Determining the magnetic field vector in quiescent solar prominences is possible by interpreting the Hanle and Zeeman effects in spectral lines. However, observational measurements are scarce and lack high spatial resolution. Aims. We determine the magnetic field vector configuration along a quiescent solar prominence by interpreting spectropolarimetric Results. For the most probable magnetic field vector configuration, the analysis depicts a mean field strength of 7 gauss. We do not find local variations in the field strength except that the field is, on average, lower in the prominence body than in the prominence feet, where the field strength reaches ∼25 gauss. The averaged magnetic field inclination with respect to the local vertical is ∼77 • . The acute angle of the magnetic field vector with the prominence main axis is 24 • for the sinistral chirality case and 58 • for the dextral chirality. These inferences are in rough agreement with previous results obtained from the analysis of data acquired with lower spatial resolutions.

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“…We assume that this star is rotating uniformly on the main sequence with angular velocity 1 × 10 −4 s −1 (corresponding to a surface rotation velocity ∼ 200 km s −1 , see ref. 14) and that during the subsequent evolution the angular momentum of each spherical mass shell is conserved. (As we expect some angular momentum exchange to occur in any real star, e.g.…”

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confidence: 99%