1 / 17

Galactic Astronomy 銀河物理学特論 I overview Contents:

Galactic Astronomy 銀河物理学特論 I overview Contents: Statistical properties of galaxies in the local universe Stellar properties of galaxies Emission line diagnostics of galaxies ( 藤井 ( 慎 )) Tremonti et al. 2004, ApJ, 613, 898 Morphological properties of galaxies ( 馬渡 )

slade
Télécharger la présentation

Galactic Astronomy 銀河物理学特論 I overview Contents:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Galactic Astronomy 銀河物理学特論 I overview • Contents: • Statistical properties of galaxies in the local universe • Stellar properties of galaxies • Emission line diagnostics of galaxies (藤井(慎)) • Tremonti et al. 2004, ApJ, 613, 898 • Morphological properties of galaxies (馬渡) • Dynamical structure of galaxies (小室) • Dependence of galaxy properties on “environment” (本間) • Multi-wavelength view of galaxies (IR, 藤井(淳)) • Active galaxies and super massive black holes in the local universe • Relation between bulges and super massive black holes of galaxies (前林) • Unified model of Active Galactic Nuclei • Observations of galaxies in the distant (high-redshift universe) • Searching for distant galaxies, method (大野) • Luminosity function of galaxies and its evolution (鶴指) • Stellar mass function of galaxies (本田) • Chemical evolution of galaxies (Kogawa) • Evolution of dynamical properties of galaxies (Akhlaghi) • Co-evolution of galaxies and super massive black holes • Observational astronomy in future

  2. Galactic Astronomy銀河物理学特論 ILecture 1-2: Emission line diagnostics of galaxies Seminar: Tremonti et al. 2004, ApJ, 613, 898Lecture: 2011/10/17

  3. Regions of ionized gas 1: HII regions in M51 galaxy

  4. Regions of ionized gas 2: Narrow-line region around Active Galactic Nuclei

  5. Emission line spectra　：　 Ratios between lines vary with ionization source, temperature, density, metallicity, extinction, and so on. [OI] Ionization source = 10,000K star Electron density = 1000cm-3 Electron temperature = 7,000-25,000K Ionization source = 100,000K star Electron density = 1000cm-3 Electron temperature = 10,000K Ionization source = power-law continuum -> Various ionization levels, [OI], [OII], [OIII] Electron density = 1000cm-3 Electron temperature = 10,000K

  6. Emission line diagnostics　：　 • Ratios between lines vary with ionization source, temperature, density, metallicity, extinction, and so on. • Ionization source : Young stars or AGN ? • Line flux = amount of ionization photons • # of young stars = star formation rate • luminosity of AGN = black hole mass accretion rate • Ionization parameter : gas density vs. photon density • Metallicity (金属量) : X/H, O/H, Fe/H • (Electron) density : n_e • (Electron) temperature : T_e = ionization level • Dust extinction : from Balmer decrement

  7. Collisional excitation, metastable state (準安定準位), and forbidden lines(禁制線): case with Oxygen-atom and Oxygen-ion Upper levels have different energy: Electron temperature can be determined with the flux ratio of these lines, if electron density is lower than critical density. Upper levels are close ~ doublet: Electron density can be estimated with the flux ratio of these lines if electron density is lower than critical density.

  8. Estimation of electron density Electron density can be determined with transitions between doublet and ground state. Collisional excitation and spontaneous emission, ratio determined by “statistical weight” (統計的重み) of each state Critical density for each forbidden line. Collisional excitation and collisional de-excitation, ratio determined by “statistical weight” + “transition probability (遷移確率)” 小暮　智一　“星間物理学”

  9. Estimation of electron temperature: 小暮　智一　“星間物理学”

  10. Estimating metallicity (O/H ) : bese-line Metallicity (O/H abundance ratio) of gas-component of galaxies can be estimated with collisionally excited forbidden lines. [OII] 3729/3726, [SII] 6716/6731 -> Electron density [OIII] (4959+5007) / 4363 -> Electron temperature [OIII] / Hb + Te + ne -> O++ / H+ [OII] / Hb + Te + ne -> O+ / H+ O++ / H+ + O+ / H+ -> O / H (assuming ionized region)

  11. Sample: O/H vs. y, and y of the early universe O/H abudances are compared with y (=He/H) determined from ratio between recombination lines HeI / Hb -> y+ = He+ / H+ HeII / Hb -> y++ = He++ / H+ x(He+) / x(H+) = 1 (ionization fraction is similar for H, He) (smaller if log[(O+/S+)/(O++/S++)]>0.7) -> y+ + y++ = y (number fraction) He mass fraction Y = 4y[1-20(O/H)] / (1+4y) Pagel et al. 1992, MNRAS, 255,325

  12. Estimation of metallicity　：　“Bright line method 1” Ratio between summed flux of multiple ionization states and flux of Balmer line. R23 = ( f([OIII]4959,5007) + f([OII]3727,3729) ) / f(Hb), but two-valued function in the low-metallicity range S23 = ( f([SIII]9069,9532 + f([SII]6717,6731) ) / f(Hb), but two-valued function in the wide metallictiy range. Kewley & Dopita 2002, ApJS, 142, 35 (Originally from Pagel et al. 1980, MNRAS, 193, 219)

  13. Estimation of metallicity　：　“Bright line method 2” Metallicity estimation with one line ratio： [NII]6584 / [OII]3726,3729(affected by dust extinction) [NII]6584 / [SII]6717,6731(Saturation at low metallicity, degenerate with ionization parameter). [NII]6584 / [OIII]5007 (saturation at low metallicity, degenerate with ionization parameter, affected by dust extinction) Kewley & Dopita 2002, ApJS, 142, 35

  14. Metallicity determination ：　“Bright line method 3” Metallicity determination only with f([NII6584) / f(Ha). Kewley & Dopita 2002, ApJS, 142, 35

  15. Metallicity determination with various line ratios: Maiolino et al. 2008, A&A, 488, 463

  16. Chemical evolution model of galaxies: “1-zone”, “closed-box” model • Instantaneous Recycling Approximation = Stars are formed but soon (simultaneously) exploded, a fraction is kept as stellar remnants (lock-up as white dwarfs, black-holes, long-lived stars) and the remaining fraction is returned to the interstellar space (stellar wind, super nova remnants) as metal enriched gas. • 1-zone model = Mtotal(t) = Mgas(t) + Mstar(t) = constant, no-infall, no-outflow. • With these assumptions, the gas metallicity abundance (Z(t)) increases with the stellar mass fraction (Mstar(t)/(Mtotal(t)) • Metal mass in gas = Mgas(t) * Z(t) • Yield = P= Mgas(t) * dZ(t) / dMstar(t) : gas metallicity increase with star formation • In “closed-box” mode, Z(t) =- P ln( Mgas(t) / Mtotal(t) )

More Related