[PPT] - Fluorescent rings in RELHICs Calvin Sykes PowerPoint Presentation

SLIDE 1

Fluorescent rings in RELHICs

Calvin Sykes calvin.v.sykes@durham.ac.uk

(with M. Fumagalli, R. Cooke, T. Theuns,

A. Benítez-Llambay)

Small Galaxies, Cosmic Questions Durham, 29 July 2019

SLIDE 2

DM Gas RELHICs: Benítez-Llambay et al, 2017 Data: APOSTLE simulatjons, Sawala et al 2016

RELHICs

SLIDE 3

DM Gas RELHICs: Benítez-Llambay et al, 2017 Data: APOSTLE simulatjons, Sawala et al 2016

RELHICs

Mass too low: gas stripped away Mass too high: forms stars Just right!

SLIDE 4

DM Gas

RELHICs

Data: APOSTLE simulatjons, Sawala et. al 2016

SLIDE 5

Why does this happen?

SLIDE 6

Predicting Hɑ emission

Gas in RELHICs is illuminated by the ultraviolet background (UVB) Model this interactjon using our own radiatjve transfer code* Solve for hydrostatjc, thermal and ionisatjon equilbrium to determine Hɑ emissivity Sharp peak at ionisatjon front... …which appears ring-shaped in projectjon

*htups:/ /github.com/calvin-sykes/spherical_cloudy

Ionisatjon front High-density, but mostly neutral Highly ionised, but low-density Emissivity ( = Hɑ power per unit volume)

SLIDE 7

Predicting Hɑ emission

See Sykes et al 2019, MNRAS 487, 609-621

Gas in RELHICs is illuminated by the ultraviolet background (UVB) Model this interactjon using our own radiatjve transfer code* Solve for hydrostatjc, thermal and ionisatjon equilbrium to determine Hɑ emissivity Sharp peak at ionisatjon front... …which appears ring-shaped in projectjon

*htups:/ /github.com/calvin-sykes/spherical_cloudy

Surface brightness (= projected emissivity)

SLIDE 8

Predicting Hɑ emission

See Sykes et al 2019, MNRAS 487, 609-621

Gas in RELHICs is illuminated by the ultraviolet background (UVB) Model this interactjon using our own radiatjve transfer code* Solve for hydrostatjc, thermal and ionisatjon equilbrium to determine Hɑ emissivity Sharp peak at ionisatjon front... …which appears ring-shaped in projectjon

*htups:/ /github.com/calvin-sykes/spherical_cloudy

Ionisatjon front

SLIDE 9

What can we learn from rings?

SLIDE 10

What can we learn?

Observable propertjes of these rings are sensitjve to:

Propertjes of dark matuer (CDM/WDM, cusps/cores)
Primordial abundance of helium
Amplitude and shape of the ultraviolet background

SLIDE 11

DM properties from size of ring

Projected size of the ring is sensitjve to propertjes of DM halo Apparent size of ring is degenerate with distance and halo mass

Core radius (N.B.: models shown here are illustratjve only!)

SLIDE 12

Combined constraints from Hɑ + HI 21cm

Can break this degeneracy if HI profjle is also known Within a family of models, profjles are steeper for higher masses Combining ring size, brightness, and profjle slope can uniquely determine DM profjle

Sykes+ 2019a, MNRAS

SLIDE 13

Primordial helium from fmux ratios

Rings are expected for helium recombinatjon lines too! Comparing Hɑ and He integrated fmux gives yp to within 1% precision Compared to using H II regions: – fully in low density regime – no stellar contaminatjon

Sykes+ 2019b, in prep

SLIDE 14

Primordial helium from fmux ratios

Rings are expected for helium recombinatjon lines too! Comparing Hɑ and He integrated fmux gives yp to within 1% precision Compared to using H II regions: – fully in low density regime – no stellar contaminatjon

Sykes+ 2019b, in prep

...to recover this value of yp…

Measure this...

...to this level

f precision

SLIDE 15

UVB intensity from brightness of ring

UVB is diffjcult to constrain at low-z due to stellar contaminatjon Star-free RELHICs provide a solutjon: Hɑ ring brightness is directly proportjonal to UVB intensity

increasing projected radius

Sykes+ 2019a, MNRAS

SLIDE 16

Are they actually detectable?

SLIDE 17

Number density of rings in LG

Rings are rare: expect ~few per Apostle volume Impractjcal to fjnd around MW, but surveying comparable volume much easier around other galaxies

Sykes+ 2019a, MNRAS

SLIDE 18

Detection strategy

Higher-mass RELHICs are bright HI emituers detectable in deep HI surveys Followup with deep imaging to rule out stellar component, then search for Hɑ with MUSE

SLIDE 19

Summary

Hɑ emission from massive RELHICs appears ring-shaped in projectjon Propertjes of rings are sensitjve to UVB, halo mass and density profjle, and yp Observing a ring would allow these to be constrained

Sykes et al 2019, MNRAS 487, 609-621

Primordial helium abundance DM mass and propertjes UVB intensity

SLIDE 20

ENGinE

Suite of 50 Mpc/h boxes at same resolutjon as EAGLE high-res (Mbar=2.3x105 M☉) Aim: do RT in postprocessing and look at distributjon, propertjes of HI absorbers

EAGLE-25Mpc

SLIDE 21

Extra slides

SLIDE 22

Surface brightness always maximal at NHI~1019cm-2 This coincides with the ionisatjon front Provides a “fjxed point” despite substantjal variatjon in profjle size and shape

Self-similarity in profjles

Curves are for difgerent M200, UVBs, halo profjles increasing projected radius

19

SLIDE 23

Tests of our RT code

SLIDE 24

Mass range for which rings appear

SLIDE 25

UVB slope

SLIDE 26

SLIDE 27

SLIDE 28

Fluorescent rings in RELHICs

Calvin Sykes calvin.v.sykes@durham.ac.uk

(with M. Fumagalli, R. Cooke, T. Theuns,

RELHICs

RELHICs

RELHICs

Why does this happen?

Predicting Hɑ emission

Predicting Hɑ emission

Predicting Hɑ emission

What can we learn from rings?

What can we learn?

Observable propertjes of these rings are sensitjve to:

DM properties from size of ring

Projected size of the ring is sensitjve to propertjes of DM halo Apparent size of ring is degenerate with distance and halo mass

Combined constraints from Hɑ + HI 21cm

Can break this degeneracy if HI profjle is also known Within a family of models, profjles are steeper for higher masses Combining ring size, brightness, and profjle slope can uniquely determine DM profjle

Primordial helium from fmux ratios

Rings are expected for helium recombinatjon lines too! Comparing Hɑ and He integrated fmux gives yp to within 1% precision Compared to using H II regions: – fully in low density regime – no stellar contaminatjon

Primordial helium from fmux ratios

Rings are expected for helium recombinatjon lines too! Comparing Hɑ and He integrated fmux gives yp to within 1% precision Compared to using H II regions: – fully in low density regime – no stellar contaminatjon

UVB intensity from brightness of ring

UVB is diffjcult to constrain at low-z due to stellar contaminatjon Star-free RELHICs provide a solutjon: Hɑ ring brightness is directly proportjonal to UVB intensity

Are they actually detectable?

Number density of rings in LG

Rings are rare: expect ~few per Apostle volume Impractjcal to fjnd around MW, but surveying comparable volume much easier around other galaxies

Detection strategy

Higher-mass RELHICs are bright HI emituers detectable in deep HI surveys Followup with deep imaging to rule out stellar component, then search for Hɑ with MUSE

Summary

Hɑ emission from massive RELHICs appears ring-shaped in projectjon Propertjes of rings are sensitjve to UVB, halo mass and density profjle, and yp Observing a ring would allow these to be constrained

ENGinE

Suite of 50 Mpc/h boxes at same resolutjon as EAGLE high-res (Mbar=2.3x105 M☉) Aim: do RT in postprocessing and look at distributjon, propertjes of HI absorbers

Extra slides

Surface brightness always maximal at NHI~1019cm-2 This coincides with the ionisatjon front Provides a “fjxed point” despite substantjal variatjon in profjle size and shape

Self-similarity in profjles

19

Tests of our RT code

Mass range for which rings appear

UVB slope

ENGinE halo mass function