Mesurer la formation d'étoiles dans les galaxies - David Elbaz - Free

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OII H8 H10 H9 Hδ CaIIH&K Raies de Balmer et taux de formation d'étoiles late-type Spiral (Sc) (with open arms) Hγ OIII Hβ OIII Elliptical early-type Spiral (Sa) (with proeminent bulge) Hα Irregular Galaxies J1 - David Elbaz Mesurer la formation d'étoiles dans les galaxies Page 6
Discontinuité de Balmer (Balmer break) et discontinuité à 4000 Å (D4000, 4000Å break) The Balmer break and the 4000 Å break are often treated as one feature, due to their similar locations and the fact that they partially overlap. However, the breaks originate from different physical processes and behave differently as populations age. Both breaks are due to absorption in the atmosphere of stars. The 4000 Å break arises because of an accumulation of absorption lines of mainly ionized metals. As the opacity increases with decreasing stellar temperature, the 4000 Å break gets larger with older ages, and it is largest for old and metal-rich stellar populations. The metallicity is of minor influence for populations with ages less than 1 Gyr (Bruzual & Charlot 2003). Bruzual A. (1983) proposed D(4000), which measures the ratio of the average flux density Fν in the bands 4050–4250 Å and 3750–3950 Å around the break. Because of the broad regions, this index is fairly sensitive to reddening by dust. To reduce this effect, Balogh et al. (1999) defined a new index Dn(4000) that was based on smaller continuum regions (4000–4100 and 3850–3950 Å). The Balmer break at 3646 Å marks the termination of the hydrogen Balmer series and is strongest in A-type stars. Therefore, the break strength does not monotonically increase with age, but reaches a maximum in stellar populations of intermediate ages (0.3–1Gyr). The strength of the Balmer sequence can be best measured from the individual Balmer lines, such as Hδ.
Page 1 and 2: Mesurer la formation d’étoiles d
Page 3 and 4: The spectra tell us: • The galaxy
Page 5: Absorption: Ca(H) 3933.7Å Ca(K) 39
Page 9 and 10: Discontinuité de Lyman (Lyman-brea
Page 11 and 12: Propriétés des étoiles sur la s
Page 13 and 14: Emission de l'ISM: raies en émissi
Page 15 and 16: Galaxies J1 - David Elbaz Mesurer l
Page 17 and 18: Mesure observationnelle du taux de
Page 19 and 20: Rayonnement de l'hydrogène dans l'
Page 21 and 22: Relation taux de formation d'étoil
Page 23 and 24: HII HII+poussière Etoile HI+poussi
Page 25 and 26: Le milieu interstellaire (ISM) de l
Page 27 and 28: 4 types d'émission : Régions HII
Page 29 and 30: Le cas des raies de Lyman et de Bal
Page 31 and 32: Efficacité d'absorption des photon
Page 33 and 34: Information issue de la largeur éq
Page 35: Relation taux de formation d'étoil
Page 38 and 39: intensité SFR vs age, metallicity
Page 40 and 41: Corriger Hα de l'extinction grâce
Page 42 and 43: Corriger l'émission UV de l'extinc
Page 44 and 45: Hα et IR: le cas des starbursts…
Page 46 and 47: Hα et IR: le cas des starbursts…

Mesurer la formation d'étoiles dans les galaxies - David Elbaz - Free

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