AGA5802 Spectroscopy

Transcription

1 Introduction AGA5802 Spectroscopy Basic information about different type of spectrographs Prism Gratings Applications Bibliography: To Measure the Sky, Kitchin, Lena and others... Prof. Jorge Meléndez 1

2 Treinamento de redução de espectros 16/abril? Bring your laptop with IRAF installed (preferred option) or take notes and do it later on your desktop computer Dataset will be available online or in a pendrive 2

3 Install IRAF on linux (or a Mac) Linux Se prefere Ubuntu, recomendo Ubuntu LTS (Long Term Support: five years from April 2012). Opções: - Particionar o disco (1 partição para o linux) - Only linux - Instalar linux dentro do windows como uma Virtual machine (e.g. Oracle Virtual Box) 3

4 IRAF Instalação automática para Ubuntu LTS Fernando A. Avila Castro Get.iso file from: - Mount.iso file - Enable universe and multiverse repositories: For older Ubuntu versions or further tips check: 4

5 Fotometria vs. Espectroscopia 5

6 August Comte was one of the most influential French philosophers of the first half of the 19th century. Comte held that there were limits to what we could know, principally set by the constraints on how much information we could gather. He thought that the chemical composition of the stars was a prime example of "unobtainable knowledge" because the stars were so distant that we could never get samples of their material to examine. We can never know what the stars are made of, Comte gloomily concluded in 1835: On the subject of stars, all investigations which are not ultimately reducible to simple visual observations are necessarily denied to us We shall never be able by any means to study their chemical composition 6

7 Continuous (optical) spectrum Line spectrum Infrared spectrum William Herschel (1800) Newton (1666) Fraunhofer (1817) 574 lines Emission spectrum John Herschel (son of William) and W.H. Fox Talbot (1826) Wollaston (1802) 7 lines

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10 Fraunhofer found 574 lines in the solar spectrum (1817) 10

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12 Fraunhofer, father of astronomical spectroscopy 12

13 Joseph Fraunhofer ( ), in Denkschriften der Königlichen Akademie der Wissenschaften zu München With the same device [i.e., spectroscope], I've also made some experiments on the light of some stars of the first magnitude. Since the light of these stars is many times weaker than that of Venus, so naturally the brightness of the spectrum is also many times less. Notwithstanding, I have seen -- without any illusion -- three broad stripes in the spectrum of Sirius, which seem to have no similarity to those of sunlight; one of these stripes is in the green, and two in the blue. Also, in the spectrum of the light of other fixed stars of the first magnitude, one detects stripes; yet these stars, in regard to the 13 stripes, seem to differ among themselves.

14 Caraterísticas dos espectros - Wavelength l,frequency n ou velocity v - Spectral resolution: Dl, Dn, Dv Dl, Dn, Dv : elemento de resolução espectral em comprimento de onda, frequência ou velocidade - Resolving power : R R = l/dl, R = n/dn, R = c/dv - Spectral coverage : l min - l max 14

15 Low spectral resolution (Dl 1 Å) vs. High spectral resolution (Dl ~ 0,1 Å) Spectral coverage : Å 15

16 Dv = 1,35km/s R =

17 A few examples R ~ , HRS (HET/McDonald) single-object 17

18 A few examples 18

19 R ~ 7000, DEIMOS (Keck) multi-object 1,1 Mpc 19

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21 Terminology for spectral lines FWHM Lena 3 rd Ed. Lena Fig. 5.1 in 2 nd Ed. 21

22 Slide adatado da Prof. Claudia (INPE) As linhas espectrais carregam muitas informações dos processos e das condições físicas existentes na fonte (Processos Radiativos). Alguns exemplos: Velocidade radial, planetas Perfil, FWHM Fluxo relativo Rotação Atividade estelar 22

23 Exemplos de linhas espectrais Lena 3 rd Ed or Table nd Ed. 23

24 Resolução espectral Lena 3 rd Ed 24