ALMA The Effects of Far UV - PowerPoint PPT Presentation

大向 一行 兼 初代星初代銀河研究会 ALMA 時代の宇宙構造形成理論 The Effects of Far UV & Cosmic Rays on HD Cooling in Population III.2 Star Formation 仲内 大翼（京都大学 , D1 ） 稲吉 恒平 Sat, 26 Jan. 2013

§1. Introduction §2. Self-Gravitating Clouds in Relic HII Regions §3. Shock-Experienced Gas Clouds §4. Summary

§1. Introduction

Population III.2 Population III.1 : the very first stars formed from primordial gas Population III.2 : stars formed from primordial gas that has been affected by other stars ★ Under what environments would Pop III.2 stars be born ? ★ 1) Relic HII region ionized ! 2) Shock-experienced gas cloud (virialization shock or supernova remnant shock). with External Radiation, Cosmic Ray Irradiation etc. HII region Relic HII region SNR shock in a halo Pop III.1

Pop III.1 vs Pop III.2 10 4 ★ III.1 : formed from neutral gas H2 cooling dominates all the way. H2 10 3 III.1 ★ III.2 : T [ K ] formed from ionized primordial gas 10 2 HD III.2 H + e − → H − + γ 1 10 4 M � H2 H − + H → H 2 + e − 10 3 M � 10 2 M � 2 19 10 M � + 10 1 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 n [ cm -3 ] � � � � gas is cooled to ~ 100 K ★ Fragment mass scales � � � � 3 / 2 � � � � T n � − 1 / 2 HD M J , III . 1 ∼ 10 3 M � D + + H 2 → HD + H + . 10 4 cm − 3 200 K � 3 / 2 � � HD cooling dominates for T < 100 K � − 1 / 2 T n M J , III . 2 ∼ 40 M � 10 5 cm − 3 50 K cooled up to ~ T CMB ( z ) Pop III.2 : e.g., Uehara & Inutsuka 00 Possibility of low-mass zero-metal star Nakamura & Umemura 02

Effects of External Radiation and CRs ★ Lyman - Werner (11.2 - 13.6 eV) Ultra Violet radiation Photodissociation of H2 and HD molecules. H 2 + γ → 2H Suppressed ! → HD + γ → H + D H + e − → H − + γ 1 ★ External Radiation with energy > 0.75 eV H − + H → H 2 + e − 2 → + H − + γ → H + e − + negative feedback for cooling ★ Cosmic Ray irradiation Activated ! Photoionization of H atoms. H + e − → H − + γ 1 − + → H + CR → e − + H + H − + H → H 2 + e − 2 + positive feedback for cooling

Can HD cooling dominate in Pop III.2 formation ? J 21 , crit ∼ 0 . 01 is enough to suppress HD cooling. Yoshida +07, � � Wolcott-Green & Haiman 11 J J 21 ≡ 10 − 21 erg / cm 2 / s / Hz * Background FUV intensity : e.g., Trenti + 09 − @ s J 21 ∼ 0 . 1 − 1 z ∼ 10 Is HD cooling minor contributor !? However, only negative feedbacks were considered ! Positive feedbacks should also be considered ! ★ CRs irradiation → positive feedback for HD cooling y J 21 , crit →

Our Study ★ Thermal evolutions of gas clouds under the irradiation of FUV and CRs are calculated. n � 10 7 cm − 3 Focusing on low-density ( ) regions. ★ Pop III.2 star formation in 1) self-gravitating clouds in relic HII regions 2) shock-experienced gas cloud are considered. Quantitatively discuss when HD cooling can be the dominant cooling process in primordial gas.

§2. Self-Gravitating Clouds in Relic HII Regions

で計算し直すべき で計算し直すべき Thermal Evolution of Self-Gravitating Clouds in Relic HII Regions Relic HII region ★ one-zone model HII region in a halo d ρ � � de dt = − P d 1 − Λ net dt = ρ , t ff dt ρ ρ Pop III.1 ★ Initial Conditions Yoshida + 07 Whalen + 04 f n 0 = 0 . 3 cm − 3 ts T 0 ∼ 10000 K Kitayama + 04 No CR � 19 = 0.0 10 4 J21 = 0.0 No FUV & CR case J21 = 0.01 J21 = 0.1 J21 = 1 HD cooling dominates. J21 = 10 10 3 H2 only T [ K ] FUV irradiation : J21 FUV 10 2 HD-domi. HD cooling is suppressed for 10 4 M � 10 3 M � 10 2 M � 19 10 M � J 21 � 0 . 02 10 1 * * 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 J 21 , bg ∼ 0 . 1 − 1 n [ cm -3 ]

★ ★ When does HD cooling dominate ? With CRs J 21 = 0.1 relic HII region � 10 4 10 4 10 4 � 19 = 0.0 n 0 = 0.03 0.1 (fiducial) n 0 = 0.3 1.0 n 0 = 3 10 3 10 theory 100 10 3 10 3 J crit H2 only 10 2 HD cooling T [ K ] suppressed J 21 10 1 10 2 CR 10 2 HD-domi. 10 4 M � 10 0 10 3 M � 10 2 M � HD cooling 19 10 M � 10 1 10 1 dominated 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 -1 10 -1 n [ cm -3 ] CR irradiation : ζ 19 10 -2 10 -1 10 0 10 1 10 2 10 3 the CR int � 19 10 − 19 s − 1 . normalized by HD cooling dominates. For ζ 19 � 3 ζ 19 � 5 CR effect independent of initial conditions. J crit ζ 19

§3. Shock-Experienced Gas Clouds

とかもやるべき、後者の場合 になってしまう は計算済み は計算済み とかもやるべき、後者の場合 になってしまう Shock-Experienced Gas Clouds shock ★ virialization shock : cooled layer γ γ v infall c T c � 1 / 3 � 1 + z vir � 1 / 2 � M vir n c r ∼ 20 km / s . 10 7 h − 1 M � 15 ρ , v, T ρ 0 , v 0 ρ 1 , v 1 , T ∼ H/c post pre 1 , T 1 , v, T t cross ∼ H/c s ( T c ) � ★ Post-shock flow : 1-D strong steady shock t ff ∼ 1 / G ρ c ρ 1 v 1 = ρ v, P ( ρ ) = 4 � 1 − 3 ρ 1 � → const. 3 ρ 1 v 2 1 4 ρ 1 + P 1 = ρ v 2 + P, c T → T c t ff � t cool ρ 1 v 2 n → n c ρ T ∝ ρ − 1 � 1 � de dt = − P d − Λ net , dt ρ ρ Formation and growth of cooled layer becomes fragment n c c T c the cooled layer with self-gravitated & ∼ H/c contract t cross � t ff t cross ∼ t ff t cross � t ff t cross

は計算済み とかもやるべき、後者の場合 になってしまう は計算済み とかもやるべき、後者の場合 になってしまう Thermal Evolution of the Post Shock Flow ★ After : one-zone model t cross � t ff No CR � 19 = 0, n 0 = 0.1, v 0 = 40, y 0 (e) = 10 -2 10 4 d ρ � � de dt = − P d 1 − Λ net dt = ρ J21 = 0.0 , J21 = 0.01 t ff dt ρ ρ J21 = 0.1 J21 = 1 J21 = 10 ★ Initial Conditions 10 3 H2 only y n 0 = 0 . 1 cm − 3 , t v 0 = 40 km / s. isobaric 10 2 M � T [ K ] FUV 10 2 No FUV & CR case 10 4 M � c T c HD-domi. HD cooling dominates. 10 3 M � 19 10 M � 10 1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 n c FUV irradiation : J21 n [ cm -3 ] ★ In relic HII region case, HD cooling is suppressed for J 21 � 0 . 1 HD cooling is suppressed for J 21 � 0 . 02 shock experienced gas is favorable for efficient HD cooling.

右上： を変えた時の であ 右下： 左下： としている。左上： におけるガスの熱進化の違い。 を変えた時の 。 ★ ★ の等高線。左上から ★ る。斜め点線は であ る。斜め点線は の等高線。左上から 右下： 左下： としている。左上： 。 右上： におけるガスの熱進化の違い。 When does HD cooling dominate ? With CRs shock compressed gas J 21 = 1.0, n 0 = 0.1, v 0 = 40, y 0 (e) = 10 -2 10 4 10 4 (fiducial) v 0 = 40, n 0 = 0.1 � 19 = 0.0 v 0 = 40, n 0 = 1 0.1 v 0 = 20, n 0 = 0.1 1 10 3 HII 10 100 theory 10 3 10 2 H2 only HD cooling T [ K ] suppressed J 21 10 1 CR c T c 10 2 n 0 HD-domi. 10 4 M � 10 0 HD cooling (fiducial) 10 3 M � y v 0 dominated 10 2 M � 19 10 M � n c 10 -1 10 1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 n [ cm -3 ] 10 -2 10 -1 10 0 10 1 10 2 10 3 CR irradiation : ζ 19 � 19 ζ 19 J crit For HD cooling dominates. 1 ζ 19 � 10 ζ 19 � 20 CR effect ★ n 0 J crit ( ζ 19 � 20) independent of initial conditions. y v 0 J crit ( ζ 19 � 20)