Ly Emission in Low Metallicity Galaxies at z ~2 Dawn Erb - - PowerPoint PPT Presentation

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ly emission in low metallicity galaxies at z 2
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Ly Emission in Low Metallicity Galaxies at z ~2 Dawn Erb - - PowerPoint PPT Presentation

Aug 11, 2023 257 likes •499 views

Ly Emission in Low Metallicity Galaxies at z ~2 Dawn Erb University of Wisconsin-Milwaukee Tokyo Spring Cosmic Ly Workshop March 27, 2018 Collaborators Danielle Berg University of Wisconsin-Milwaukee Ohio State University Naveen

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Ly𝛃 Emission in Low Metallicity Galaxies at z~2

Dawn Erb University of Wisconsin-Milwaukee

Tokyo Spring Cosmic Ly𝛃 Workshop March 27, 2018

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Collaborators

Danielle Berg University of Wisconsin-Milwaukee Ohio State University Chuck Steidel (Caltech) Max Pettini (Cambridge) Allison Strom (Carnegie) Ryan Trainor (Franklin & Marshall) Naveen Reddy (UC Riverside) Alice Shapley (UCLA) Gabriel Brammer (STSci) David Kaplan (UW-Milwaukee)

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Ly𝛃 emission stronger at low metallicity

−2.0 −1.5 −1.0 −0.5 0.0 0.5

Log ([N II]/Hα)

−1.0 −0.5 0.0 0.5 1.0

Log ([O III]/Hβ)

Extreme KBSS Green Peas −1.8 −1.6 −1.4 −1.2 −1.0 0.7 0.8 0.9 1.0

Erb et al 2016 see also Trainor et al 2016

−60 −40 −20 20 40 60 80 100 120 140 160 180 Lyα equivalent width (˚ A) 0.000 0.005 0.010 0.015 0.020 0.025 0.030 Relative number

Extreme KBSS Green Peas

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Relationships between strength and line profile

Erb et al 2014

Ly𝛃 equivalent width anti-correlated with velocity offset Double peaks unresolved at low resolution

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Diversity among Ly𝛃-emitters

Law et al 2012

Q2343-BX418 M★= 2 x 109 M⦿ SFR = 50 M⦿ yr-1 SSFR = 18 Gyr-1 12 + log(O/H) = 8.08 (Te) O32 = 9.66 Q2343-BX660 M★= 5 x 109 M⦿ SFR = 23 M⦿ yr-1 SSFR = 4 Gyr-1 12 + log(O/H) = 8.13 (Te) O32 = 10.98

3 arcsec HST WFC3 F160W O/H, O32 from Steidel et al 2014

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Ly𝛃 profile variations

−3000 −2000 −1000 1000 2000 3000 Velocity (km s−1) 2 4 6 8 10 12 14 16 18 Normalized Flux

BX418 with VLT XSHOOTER R=6200 Archival data, Terlevich et al 2015

BX418 BX660

−2000 −1500 −1000 −500 500 1000 1500 2000 Velocity (km s−1) 1 2 3 4 5 Flux

LRIS 600-line grism Erb et al 2018a, in prep

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−2000 −1000 1000 2000 3000 Velocity (km s−1) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Normalized Flux

Absorption lines trace variations in outflows

Si IV λ1394 Si IV λ1403

BX418 BX660

Erb et al 2018a, in prep

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Absorption lines trace variations in outflows

−1500−1000 −500 500 1000 1500 Velocity (km s−1) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Normalized Flux −1500−1000 −500 500 1000 1500 Velocity (km s−1) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 −1500−1000 −500 500 1000 1500 Velocity (km s−1) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 −1500−1000 −500 500 1000 1500 Velocity (km s−1) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Si II λ1260 Si II λ1304 O I λ1302 C II λ1334 Si II λ1527

BX418 BX660

Erb et al 2018a, in prep

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Analysis of larger sample underway

C II λ1334

1200 1205 1210 1215 1220 1225 1230 Rest Wavelength (˚ A) 2 4 6 8 10 12 14 16 18 Flux density (µJy) Q0142-BX165 WLyα = 61 ˚ A 1200 1205 1210 1215 1220 1225 1230 Rest Wavelength (˚ A) 1 2 3 4 5 6 Flux density (µJy) Q0207-BX144 WLyα = 38 ˚ A 1200 1205 1210 1215 1220 1225 1230 Rest Wavelength (˚ A) 2 4 6 8 10 Flux density (µJy) Q0207-BX74 WLyα = 102 ˚ A 1200 1205 1210 1215 1220 1225 1230 Rest Wavelength (˚ A) 1 2 3 4 5 Flux density (µJy) Q0207-BX87 WLyα = 78 ˚ A

Erb et al 2018a, in prep

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Implications and next steps

Otherwise similar low metallicity galaxies have varying CGM properties: relevant to LyC escape Low metallicity and high ionization necessary but not sufficient Expanding the sample: what can we learn from the most extreme objects? New results from KCWI: what can we learn from integral field spectroscopy?

2 1

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Low metallicity and high ionization at z=1.85

Berg et al 2018, arxiv:1803.02340

1

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Ly𝛃 emission does not require outflows

Berg et al 2018, arxiv:1803.02340

See also Jaskot et al 2017

−1000 −500 500 1000 Velocity km s−1 0.6 0.8 1.0 1.2 1.4 1.6 Normalized Flux

Average Absorption Low Ionization High Ionization OIII] λ1660 OIII] λ1666

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Narrowband Ly𝛃 imaging with HST

Ly𝛃 + continuum Off-line continuum Continuum-subtracted Ly𝛃

Spectroscopic slit losses ~30% Ly𝛃 equivalent width 190 Å, escape fraction ~10% Differential lensing magnification?

Erb et al 2018b, in prep

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Spatially extended Ly𝛃

Erb et al 2018b, in prep

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Q2343-BX418 with KCWI

30 kpc Erb et al 2018c, in prep

2

preliminary

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Q2343-BX418 with KCWI

30 kpc Erb et al 2018c, in prep

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Mapping the Ly𝛃 peak ratio

Erb et al 2018c, in prep

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Mapping the Ly𝛃 peak ratio

∆vpeak = 600 km s−1

Erb et al 2018c, in prep

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Mapping the Ly𝛃 peak ratio

∆vpeak = 450 km s−1

Erb et al 2018c, in prep

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Mapping the Ly𝛃 peak separation

Erb et al 2018c, in prep

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What does it mean?

Spatial variations in Ly𝛃 profile depend on

  • column density and covering fraction of neutral hydrogen
  • variations in outflow velocity, including projection effects

Full modeling required

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Summary

emission stronger at low metallicity, but CGM properties vary widely Important for LyC escape Low metallicity and high ionization necessary but not sufficient

−3000 −2000 −1000 1000 2000 3000 Velocity (km s−1) 10 20 30 40 Normalized Flux

Q2343-BX418 Q2343-BX660 SL2S J0217

Next steps: Quantify diversity in low mass samples Expand dynamic range to most extreme objects Map the CGM with emission Ly𝛃 Ly𝛃