The observed mass profiles of dark halos and the formation epoch of galaxies

Shinji Sato, Fumie Akimoto, Akihiro Furuzawa, Yuzuru Tawara, Manabu Watanabe, Yasuki Kumai

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

We have determined the mass profiles of dark halos in 83 objects observed by ASCA. The point-spread function of the X-ray telescope was deconvoled by the Richardson-Lucy algorithm, and the temperature profiles were calculated to obtain the mass profiles. The derived mass profiles are consistent with the Navarro, Frenk, & White model in (0.01-1.0)rvirial. We found a good correlation between the scale radius rs and the characteristic mass density δc, which indicates the self-similarity of dark halos. The spectrum index of primordial density fluctuation, P(k) ∝ kn, was determined from the slope of the rsc relation. For M200 = 1012-1015 M, our analysis gives n = -1.2 ± 0.3 with a confidence level of 90%. The mass density of dark halos is a good indicator of the mean mass density of the universe at the time when the halos were assembled, z = zf. Assuming δc ∝ (1 + zf)3, we have determined the epoch when each dark halo was assembled. Our analysis indicates that the field elliptical galaxies and groups of galaxies formed approximately at 1 - zf ≃ 15 and at 1 + zf ≃ 7-10, respectively.

Original languageEnglish
Pages (from-to)L73-L76
JournalAstrophysical Journal
Volume537
Issue number2 PART 2
Publication statusPublished - 10-07-2000

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halos
time measurement
galaxies
profiles
elliptical galaxies
point spread functions
temperature profile
temperature profiles
confidence
universe
telescopes
slopes
radii
x rays
analysis

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Sato, S., Akimoto, F., Furuzawa, A., Tawara, Y., Watanabe, M., & Kumai, Y. (2000). The observed mass profiles of dark halos and the formation epoch of galaxies. Astrophysical Journal, 537(2 PART 2), L73-L76.
Sato, Shinji ; Akimoto, Fumie ; Furuzawa, Akihiro ; Tawara, Yuzuru ; Watanabe, Manabu ; Kumai, Yasuki. / The observed mass profiles of dark halos and the formation epoch of galaxies. In: Astrophysical Journal. 2000 ; Vol. 537, No. 2 PART 2. pp. L73-L76.
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Sato, S, Akimoto, F, Furuzawa, A, Tawara, Y, Watanabe, M & Kumai, Y 2000, 'The observed mass profiles of dark halos and the formation epoch of galaxies', Astrophysical Journal, vol. 537, no. 2 PART 2, pp. L73-L76.

The observed mass profiles of dark halos and the formation epoch of galaxies. / Sato, Shinji; Akimoto, Fumie; Furuzawa, Akihiro; Tawara, Yuzuru; Watanabe, Manabu; Kumai, Yasuki.

In: Astrophysical Journal, Vol. 537, No. 2 PART 2, 10.07.2000, p. L73-L76.

Research output: Contribution to journalArticle

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AB - We have determined the mass profiles of dark halos in 83 objects observed by ASCA. The point-spread function of the X-ray telescope was deconvoled by the Richardson-Lucy algorithm, and the temperature profiles were calculated to obtain the mass profiles. The derived mass profiles are consistent with the Navarro, Frenk, & White model in (0.01-1.0)rvirial. We found a good correlation between the scale radius rs and the characteristic mass density δc, which indicates the self-similarity of dark halos. The spectrum index of primordial density fluctuation, P(k) ∝ kn, was determined from the slope of the rs-δc relation. For M200 = 1012-1015 M⊙, our analysis gives n = -1.2 ± 0.3 with a confidence level of 90%. The mass density of dark halos is a good indicator of the mean mass density of the universe at the time when the halos were assembled, z = zf. Assuming δc ∝ (1 + zf)3, we have determined the epoch when each dark halo was assembled. Our analysis indicates that the field elliptical galaxies and groups of galaxies formed approximately at 1 - zf ≃ 15 and at 1 + zf ≃ 7-10, respectively.

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Sato S, Akimoto F, Furuzawa A, Tawara Y, Watanabe M, Kumai Y. The observed mass profiles of dark halos and the formation epoch of galaxies. Astrophysical Journal. 2000 Jul 10;537(2 PART 2):L73-L76.