Observational Astrophysics II: May-June, Observational Astrophysics II (L2) Getting our NIRF What do want to do? 1.Image a selected spiral galaxy in H  6563 (HII/slit position) 2.Spectroscopy of HII regions => los radial velocities 3.Imaging in JHK => isophotes => deprojection => V rad (r) => rotation curve and => stellar population from colours

Observational Astrophysics II: May-June, Spectrograph Slit Radial Distance, r (arcsec to kpc) Error Bars ???!

Observational Astrophysics II: May-June, The Spiral Galaxy M83 in broad band R in narrow band H  H II regions – point likeStellar pop - extended

Observational Astrophysics II: May-June, HH line-to-continuum contrast In narrow band filter continuum U B V R I

Observational Astrophysics II: May-June, Example of long-slit observation (spatio-spectral mapping) 1´´ wide 2´ long spectrograph slit star supersonic jet flow

Observational Astrophysics II: May-June, K-spectrum of Serpens SMM1 jet (VLT-ISAAC) rovibrational H 2 lines Spatial Domain Spectral Domain1´´ slit star 2´ slit S(3) =2-1 S(2) =2-1 R = 400

Observational Astrophysics II: May-June, R = 400 (  v = 750 km s -1 ) R = (  v = 3 km s -1 ) Radial velocity measurement

Observational Astrophysics II: May-June, Observing our galaxies 1. ALFOSC H  imaging What Filter? = 6563 (z + 1) Å z (Å)

Observational Astrophysics II: May-June, Observing our galaxies 2. ALFOSC H  spectroscopy What slit width? ALFOSC Slits The following slits are available for use with ALFOSC: Simple, long-slit, covering the full spatial field of view of the instrument (in arcsec): 0.4, 0.5, 0.75, 1.0, 1.2, 1.3, 1.8, 2.5, 5.0, 10.0 Long-slit spectra are oriented vertically on the detector. The 1.8" slit is not very smooth and shows considerable flux variations along the slit.

Observational Astrophysics II: May-June, Observing our galaxies 2. ALFOSC H  spectroscopy What spectral resolution? Sun at 8.5 kpc 250 km s - 1  =  v/c R =   v (km s -1 )  (Å) R > 650< 10

Observational Astrophysics II: May-June, Observing our galaxies 2. ALFOSC H  spectroscopy What integration times? 1. NOT (or ESO) Exposure Time Calculator

Observational Astrophysics II: May-June, Observing our galaxies 2. ALFOSC H  spectroscopy What integration times? 2. Manual Estimate Quantify the n s... [ for t =1s and t ~ (S/N) 2 ]

Observational Astrophysics II: May-June, source aha... IS transport diffraction electronics Obs. analysis: Reduction Calibration Informatics telluric atmospheric transport-turbulence spherical coherent - incoherent cow coherent – incoherent detection Plane Wave Two Domains: Above & Below Atmosphere

Observational Astrophysics II: May-June, Above telluric atmosphere Photons gained Source  direct emission  scattered into beam Extra-Galactic Background Galactic Background Zodiacal Background Photons lost Source  direct abs/extinction  scattered out of beam Extra-Galactic Extinction Galactic Extinction (IS) Zodiacal Extinction A good emitter is also a good absorber (Kirchoff’s law)

Observational Astrophysics II: May-June, Below telluric atmosphere Atmosphere emission extinction scattering Optics emission absorption Detector absorption emission Transmission, T Extinction,  Efficiency,  Detector Noise

Observational Astrophysics II: May-June, Collecting terms: 1. Signal degradation Atmosphere transmission T atm (%) Telescope reflectivity T tel (%) Filter transmission T filter (%) Spectrograph throughput T spec (%) Detector efficiency QE (%) 2. Noise sources Source Photons Poisson Background Photons Sky + Telescope Detector emission Thermal or Dark Current Detector Read Noise Read out noise

Observational Astrophysics II: May-June,

Observational Astrophysics II: May-June, Signal = Source flux F tel for given V, E(B-V) Similar can be done at any other filter wavelength, e.g. in the R band

Observational Astrophysics II: May-June, Sky Backgrounds are generally given in mag/arcsec 2 (surface intensity) and are treated similar to source fluxes Dark current and read-out-noise are device specific normally provided externally (manufacturer/observatory) ALFOSC CCD # x  m pixels image scale 0.19´´/pxl dark current 0.4 e - / pxl / hr ron 5.3 e - / pxl (read time 90 s) conversion * e - / ADU (high gain) well capacity ADU (~2 16, high gain) non-linearity 0.3 % QE V 0.75 * Analogue-to-Digital Unit

Observational Astrophysics II: May-June, Worked example: NOT-ALFOSC H  image Galaxy R = 13 mag E(B-V) = 0.02 mag  R = 0.02  Airmass = 2  Seeing = 1´´  Airmass = 2  Filter #49  = 50 Å eff = 6607 Å  Line-to-continuum = 1  Sky background = 18 mag

Observational Astrophysics II: May-June, Worked example: NOT-ALFOSC H  image, ctnd. Normally, one makes the computation in electrons and converts at the end. However, at the telescope, the student should watch the ADUs (linearity check).

Observational Astrophysics II: May-June, Obs. Group Filter (type / #) Grism # Slit (arcsec) Object (Name) RA 2000 (h m s) Dec 2000 ( o ´ ´´ ) Proposal.and. Finder chart (Y/N) 1 Jeanette Christoffer NGC Andrej Milan 76, 49, , 0.75, 1.0, 1.3, 2.5 NGC YYYY 3 Anna Thomas 78, , 1.0, 1.3, 2.5 NGC NNNN 4 Sven 12, 15, 17, 18, 19, 20, , 1.2, 1.3 SAO NGC 7023 B NNNN ALFOSC admits MAX check thickness!!! 7 Filters: UBVRI FASU: 6 Grisms: 5 Slits:

Observational Astrophysics II: May-June, Preparing our NIRF

Observational Astrophysics II: May-June, Before we go to the mountain...

Observational Astrophysics II: May-June, Day # meaning astronomical night