Lecture 2 Early Spectroscopic Observations Matthew Hayes Stockholm University, department of astronomy Oskar Klein Centre for Cosmoparticle Physics

Lecture 2 Overview 2.1. First observations of QSOs the obvious place to start 2.2. Star-forming galaxies 2.3. First samples of Lya observations and followup observationally cover many papers written in the ‘80s – mid ‘90s : very good! 2.4. Lya output depends upon dust and metallicity of a galaxy Every Lya observation presented in this talk is done for a UV- or Ha selected galaxy with no prior information on Lya. Not LAEs

Ultraviolet Telescopes International Ultraviolet Explorer (IUE) Hubble Space Telescope (HST) ? Galaxy Evolution Explorer (GALEX) Far Ultraviolet Spectroscopic Explorer (FUSE) International Ultraviolet Explorer (IUE) International Ultraviolet Explorer (IUE) International Ultraviolet Explorer (IUE) International Ultraviolet Explorer (IUE) Faint Object Telescope (FOT) 1977 ()

‘Faint Object Telescope’ 1977 – single sounding rocket flight 40 cm mirror R~100 spectrophotometry at 1200 – 1700 Å Microchannel analyser read realtime on ground Pointed at 3C 273 First extragalactic spectrum in vacuum UV

International Ultraviolet Explorer 1978 – more years than planned Pointed, target-by-target telescope Short and long wavelength channels R~250 spectroscopy at 1150 – 3000 Å Spectrophotometry only Large entrance window 10 x 20 arcsec ‘Quasi-global’ photometry of Lya halos

Galaxy Evolution Explorer (GALEX) 2003 – Planned for 29 months FUV + NUV (1500 and 2200Å) imagers Slitless R~200 spectroscopy: 1450 – 1700 Å Lya at z=0.195 – 0.44 First genuine survey telescope  discovery potential (found >200 LAEs)

Galaxy Evolution Explorer (GALEX) Pointed – HST, … No such thing as un-biased! We only learn about the things we point at. Blind – GALEX

Hubble Space Telescope 2.5 m primary mirror UV sensitive down to 900 Å Many cameras that could see Lya. Those that did: Goddard High Resolution Spectrograph (GHRS) Space Telescope Imaging Spectrograph (STIS) Advanced Camera for Surveys (ACS) Cosmic Origins Spectrograph (COS)

Hubble Space Telescope Cosmic origins spectrograph 1 shot spectroscopy in range 1150 – 1440 Å or 1400 – 1800 Å (G130M and G160M) Small (2.5 arcsec) entrance window R~20,000 (15 km/s) point-source resolution Also a R~1000 setting (3000 km/s) that will do the full spectral range Note that one will not get point-source spectral resolution for Lya

Hubble Space Telescope Cosmic origins spectrograph 1 shot spectroscopy in range 1150 – 1440 Å or 1400 – 1800 Å (G130M and G160M) Small (2.5 arcsec) entrance window R~20,000 (15 km/s) point-source resolution Also a R~1000 setting (3000 km/s) that will do the full spectral range Note that one will not get point-source spectral resolution for Lya Point source ~flat surface

Hubble Space Telescope Space Telescope Imaging Spectrograph Very flexible instrument 1150 – 1750 Å slit spectroscopy G140L : R<1500 over full range G140M : R ~ 18,000 over 56 Å range (Also MAMA echelle spectroscopy with R up to 200,000) Many slits between 0.05 arcsec and slitless Guaranteed to get the spectral resolution you ask for

Hubble Space Telescope Advanced Camera for Surveys The only way to image UV emission lines Large (5) filters that can capture Lya at various z (broader than conventional narrowbands, so care is needed) Dz = 0 – 0.02; 0.02 – 0.1; 0.12 – 0.2 ; … Provide the ‘global’ Lya flux, which COS & STIS will not Spatial resolution is that of HST: <0.1 arcsec at FWHM. ESO 338-IG04

The first extragalactic spectrum Sounding rocket experiment Expected Lya/Hb ~ 40 Davidsen+1977

The first extragalactic spectrum Sounding rocket experiment Expected Lya/Hb ~ 40 Observed Lya/Hb ~ 4 Davidsen+1977

The first extragalactic spectrum Davidsen+1977 Sounding rocket experiment Expected Lya/Hb ~ 40 Observed Lya/Hb ~ 4

International Ultraviolet Explorer 1978 – more years than planned Pointed, target-by-target telescope Short and long wavelength channels R~250 spectroscopy at 1150 – 3000 Å Spectrophotometry only Large entrance window 10 x 20 arcsec ‘Quasi-global’ photometry of Lya halos

First QSO observations Oke & Zimmerman C 120 Mrk 79 Hb Lya Lya/Hb ratios much lower than expected Dust absorption explains low Lya/Hb in one case, but not the other Cannot find an obvious way to make Lya/Hb < ~15

Ha / Hb La / Hb Ha/Hb=2.8 Lya/Hb = 40,20,10,5 Wu Boggess & Gull 1979 Seyfert 1 observations with IUE Most S1 have Lya/Hb lower than expectation A minority sit above the intrinsic curve Dust reddening, high density, thick HI column all affect Lya ratios. No dominant factor found Lya N V C IV Si IV C III] Mg II

Most S1 have Lya/Hb lower than expectation A minority sit above the intrinsic curve Dust reddening, high density, thick HI column all affect Lya ratios. No dominant factor found Note that while Lya/Hb is low, Lya/UV continuum is high. Charlot & Fall Å limit is exceeded, because we target AGN Wu Boggess & Gull 1979 Seyfert 1 observations with IUE

The status of high-z LAEs in 1994 Partridge & Peebles (1967) Nebulae Pritchett (1994) 1967 predictions for finding primeval galaxies by their Lya emission had not been fulfilled by 1994 P&H D+

Meier & Terlevich 1981 Starburst galaxies with the IUE Spectra are a mess Nothing is resolved Lya blended Mrk 12 Lya blended with GC Cropped and merged tables 1 & 2

Meier & Terlevich 1981 Starburst galaxies with the IUE Lya in absorption Spectra are a mess Nothing is resolved Lya blended Lya absorbed Cropped and merged tables 1 & 2

Meier & Terlevich 1981 Starburst galaxies with the IUE Lya in emisison! Cropped and merged tables 1 & 2 Spectra are a mess Nothing is resolved Lya blended Lya absorbed Lya emitted, and in most metal poor system. Far weaker than Case B Dust + HI suppresses Lya Rare in ‘normal conditions’ No primeval galaxies

Hartmann, Huchra & Geller 1984 Starburst galaxies with the IUE Statistical sample of 6 galaxies: Lya far below case B Also first discussion of HI content of similar BCGs Surface densities – /cm2 and 3-10 times larger than stellar disks Expect multiple scatterings with a little dust First to suggest extended scattering halos would reduce SB Also expect that these N HI would imply tau Lya > 10 6 if homogeneous  ‘we expect clumpy distributions of scattering material play a major role in allowing a small fraction of the Lya photons to escape’ Pardy et al 2014, HI

Hartmann, et al 1988 First ‘statistical’ sample Statistical sample of galaxies Lya/Hb and EW anticorrelated with metallicity [O/H] La / Hb Note that metal ions don’t absorb Lya by themselves Charlot & Fall 1993 [O/H] Lya EW

IUE archives (Kinney et al 1993)

IUE + large aperture optical spectra 2D-FRUTTI Calzetti+1992 All optical spectra so far have used slits Fine for Ha/Hb or [O/H] … but not fine for Lya/Hb Large aperture optical spectroscopy took a long time to compile!

Combining the IUE archive Final-final data reduction tools from ESA/NASA: Significant flux discrepancies in 40% of galaxies 3 galaxies by 30-50% 3 more find Lya absorption where +ve upper limits were reported ‘very likely the differences are due to different error analysis and cosmic ray removal technique’ Giavalisco, Koratkar & Calzetti 1996

Combining the IUE archive Hb flux La flux Lya/Hb ~ 30 Giavalisco, Koratkar & Calzetti 1996 Lya not propto Hb

Combining the IUE archive Lya/Hb = 10 (~1/3 intrinsic) Giavalisco, Koratkar & Calzetti 1996 UV slopeE(B-V) [O/H] Lya not propto Hb No clear anticorr. between La/Hb and dust / metals La / Hb

Combining the IUE archive La / Hb Lya/Hb = 10 (~1/3 intrinsic) Lya not propto Hb No clear anticorr. between La/Hb and dust / metals Giavalisco, Koratkar & Calzetti 1996 La / Hb UV slopeE(B-V) [O/H]

Combining the IUE archive Lya/Hb = 30 (intrinsic) Giavalisco, Koratkar & Calzetti 1996 UV slopeE(B-V) [O/H] Lya not propto Hb No clear anticorr. between La/Hb and dust / metals Dust corr. does not reach Lya/Hb=30 La / Hb La / Hb. corr

Combining the IUE archive Giavalisco, Koratkar & Calzetti 1996 La / Hb Lya EW UV slopeE(B-V) [O/H] Lya EW Lya not propto Hb No clear anticorr. between La/Hb and dust / metals Dust corr. does not reach Lya/Hb=30 Lya EW seems uncorrelated too.

Combining the IUE archive Giavalisco, Koratkar & Calzetti 1996 La / Hb Lya EW UV slopeE(B-V) [O/H] Lya EW Lya not propto Hb No clear anticorr. between La/Hb and dust / metals Dust corr. does not reach Lya/Hb=30 Lya EW seems uncorrelated too?

Combining the IUE archive Giavalisco, Koratkar & Calzetti 1996 { Lya/Hb, Lya EW} and { Ha/Hb, O/H } are ‘visually’ anti-correlated Dust is responsible for Lya absorption, but scatter is enormous. No correlations are stronger than ~2 sigma

Lecture 2 Summary Only 3 satellites have provided significant numbers of Lya spectra: IUE, GALEX, and HST. The IUE operated for nearly 20 years, giving ~2 new galaxies per year on average Even in QSOs, Lya seems suppressed by a factor of 10 compared to what was expected Lya very weak on average in starbursts. Dust corrections do not reach recombination values ‘Visual’ anti-correlation observed between { Lya/Hb, Lya EW} and { Ha/Hb, O/H }. Likely Lya is being destroyed by dust but there is a huge amount of scattering