F I R S T S C I E N C E W I T H Seen through the lens of: why you - - PowerPoint PPT Presentation

F I R S T S C I E N C E W I T H

Steven Finkelstein - The University of Texas at Austin

for the HETDEX team PI: Gary Hill (UT Austin) Project Scientist: Karl Gebhardt (UT Austin)

Seen through the lens of: why you should care about Lyman-alpha equivalent width distributions

T H E R E I S A M Y S T E RY AT T H E E N D O F R E I O N I Z AT I O N ! LY M A N - A L P H A C A N H E L P !

• Many models can successfully complete reionization by z~6 and

still match constraints of a significant neutral fraction at z >7.

~ ~ = - <

• ~

~ r r = -

• =

= ~ > > < = < = < <

r < - r » r = = = - = = < »

• +

t

• t

SF+15

r r <

• r

~ t r

• t

t ~ r µ +

• ~

>

• ~
• r

=

• r

r > t =

• 2

r t ) r > ~

ROBERTSON+15

Galaxies are the source fesc=10-20%, Mlim=-13, log ξion ~ 25.2

Most galaxies have very low escape fractions (<2%), with a small fraction with higher (>10%) escape fractions, and/or that fesc varies with mass/luminosity.

4 6 8 10 12 14 Redshift 48.5 49.0 49.5 50.0 50.5 51.0 51.5 52.0 Ionizing Emissivity

Total HI Ionizing Emissivity (NHI) Galaxy HI Ionizing Emissivity AGN HI Ionizing Emissivity Galaxy NHI (fesc=13%, Mlim=-13) AGN HeII Ionizing Emissivity

4 6 8 10 12 14 48.5 49.0 49.5 50.0 50.5 51.0 51.5 52.0

SF+18, in prep

T H I S L E A D S T O A D I S C R E PA N C Y W I T H T H E M E A S U R E D I O N I Z I N G E M I S S I V I T I E S

Becker & Bolton 2013

2

Direct measurements of the total ionizing emissivity This doesn’t even consider AGNs, which we know are there at z < 4!

K I L L T W O B I R D S W I T H O N E M O D E L : C O M P L E T I N G T H E I G M W I T H L O W E R G A L A X Y E S C A P E F R A C T I O N S

• 5
• 4
• 3
• 2
• 1

log fesc 0.0 0.2 0.4 0.6 0.8 1.0 P(fesc)

log Mh=7.0 log Mh=7.5 log Mh=8.0 log Mh=8.5 log Mh=9.0/9.5 log Mh=10.0

Paardekooper+15

• 22
• 20
• 18
• 16
• 14
• 12
• 10

Absolute UV Magnitude 0.0 0.2 0.4 0.6 0.8 1.0 Cumulative Ionizing Emissivity

Robertson+15 This Work z=4 z=6 z=8 z=10 0.1L*

L*

0.01L*

This leads to *very* faint galaxies being the dominant contributor

2 4 6 8 10 12 14 Redshift 0.0 0.2 0.4 0.6 0.8 1.0 Ionized Volume Filling Fraction

QHII QHeIII Robertson+15 McGreer+15

It does successfully complete reionization with <fesc> < 5%, and matches emissivity constraints

SF+18, in prep

A L L I S W E L L ?

• The constraints used in this analysis (dark pixels from

McGreer+15, emissivities from Becker+13, and Planck 2015

• ptical depth) do not prohibit this reionization history.

6 7 8 9 10 Redshift 0.0 0.2 0.4 0.6 0.8 1.0 Ionized Volume Filling Fraction

Dark Pixel Fraction Ly Clustering Ly LF Ly EW Evolution QSO Damping Wing This Work Greig+15 Robertson+15 Rosdahl+18

Existing Lyα measurements at z ~ 7 prefer a lower ionized fraction (~50%)

SF+18, in prep

First Lyα slide

LY M A N - A L P H A A S A P R O B E O F R E I O N I Z AT I O N

• Lyα photons are resonantly scattered by neutral

HI gas, and so should be a unique tracer of the evolution of the IGM neutral fraction during reionization (e.g., Miralda-Escude+98, Malhotra & Rhoads 04, 06; Dijkstra+07).

• This has often been traced by exploring the

“Lyman-alpha” fraction.

• This measure doesn’t include the continuum

brightness of the galaxy, so analyses often split into multiple bins.

• The EW distribution (P[W]) is a more

straightforward way to trace this evolution.

• Now being used, see Pentericci+2018,

Mason+2018, Jung+2018

Mason+2018

• Emission line detections at z ~ 5.5 - 6.7 from
• GOODS-N

GOODS-S

• For each mock emission line,

Ly! Equivalent Width Distribution at z ~ 6.5 from MCMC sampling

We perform this emission line simulation (described in the left) for our observations, measuring the posterior distribution of the expected number of detections as a function of S/N for e-folding scales of W0=5-200Å. For each choice of W0, we carry out 1000 Monte Carlo simulations. The figure above shows the mean expected number of detections, averaged over each set of 1000 simulations, as a function of S/N for a range of EW distributions for z 6.5. A larger choice of W0 predicts a larger number of Ly! detections. ii)We assign the simulated Lyα line strength from the assumed EW distribution i)We assign a wavelength for the Lyα line by drawing randomly from P(z) iii) determine the S/N level of the simulated Lyα line at that wavelength. λLyα = (1+zphot)×1215.67Å

Ndetection (S/N > S-# S (Signal-to-Noise) P(z)

5.0 6.0 7.0 8.0

z

P(EW)

W0=100Å

200 400 600 800 1000

EW [Å]

P (EW) exp (-EW/W0), where W0 is an exponential scale length. 5σ detection limit

Baseline measurements at lower redshift are critical to interpret these epoch of reionization Lyα results

S E E P O S T E R B Y I N TA E

T H E H O B B Y E B E R LY T E L E S C O P E D A R K E N E R G Y E X P E R I M E N T

• We’re creating the largest spectroscopic map of the distant universe through a

blind spectroscopic survey on the 10m Hobby Eberly Telescope (HET), tracing structure via Lyα emission at 1.9 < z < 3.5.

• Our instrument VIRUS is 78 spectrograph pairs (R=750 from 350nm – 550nm),

covering 1/5th of the focal plane with 35,000 fibers, which is currently being assembled on the upgraded HET (new top-end, upgrading FOV from 4’ to 22’).

• Our fiducial survey is 450 square degrees over 3 years (taken in ~6000 pointings
• f 20 minutes each) at 1/5 fill, for nearly 100 deg2 with spectra.
• Expect ~1 million redshifts from 1.9<z<3.5 via Lyα
• >1 million redshifts from 0<z<0.5 via [OII]
• HETDEX will enable the creation of a baseline dataset for comparison with high

redshift!

S E E P O S T E R B Y G A RY H I L L

THE SURVEY FIELDS

Spring field: 300 deg2 in the North (in Ursa Major) Fall field: 150 deg2 in Stripe 82

Current status: 32 working spectrographs on the

• telescope. Four new arriving every

month, VIRUS should be complete by the end of the year.

NB: At least single-band imaging data needed to constrain EWs to distinguish between LAEs at [OII] emitters (line will not be resolved).

W H E R E W E W E R E AT A Y E A R A G O :

Talk at SnowCLAW

W H E R E W E A R E AT T O D AY:

• We have been performing science verification observations in

well-known deep fields: GOODS-N, EGS and COSMOS.

• We are using the deep-field observations to help optimize our

emission-line selection algorithms, characterize detection limits.

• This is not trivial with these data!
• Currently working on optimal combination of fibers to

centroid object, matching with imaging counterpart, and

• ptimal removal of sky emission.
• We have also started general survey observations in both

spring and fall fields.

W H E R E I S T H E C O N T I N U U M C O U N T E R PA R T ?

• In fields with deep HST imaging (mlimit~28), assuming an EW scale length
• f 70 A, we should see counterparts to ~99% of our sources.
• This can be very useful for understanding the positional accuracy of our

emission line centroiding!

• Current UT undergrad Yaswant Devarakonda has been exploring this

in the CANDELS EGS field.

Conclusion: Matches at < 1” are likely correct, but not always…

T H E P O W E R O F V I R U S

• These green squares show the

layout of a deep observation (4X HETDEX depth) we performed in GOODS-N, which

• btained data in 20 IFUs.
• We cover a similar volume as

the MUSYC CDFS pointing to a similar depth (<~LLya*), in 20X less integration time!!

• Full VIRUS will cover 4X the

volume in the same amount

• f time.

Some emission lines in GOODS-N

E A R LY L O O K I N T O T H E E W D I S T R I B U T I O N

• Using the observations taken

in GOODS-N and EGS, we can take a sneak peak into the EW distribution.

• This is for the ~70 sources

with a continuum match within 1” with W0 > 20 A.

• There are ~20 others in

this sample, but need further reliability checks.

1.0 1.5 2.0 2.5 3.0 3.5 4.0 log Rest-Frame EW 2 4 6 8 10 12 14 Number

HETDEX MUSYC

Due to current high SNR requirements Are these real?!?

Malhotra & Rhoads 2002

Here are some sources with W > 300 A, and a counterpart with a matching photo-z

What does this mean? More work needs to be done to verify, but it could indicate that the EW distribution extends out to higher values than previously thought. *If* this is true, we will characterize this extremely well with HETDEX.

Physical explanations? Extreme starbursts, AGN, low metallicities, other causes of increased ionization (top-heavy IMF, binary stars, etc), more inclusive of lower-SB emission?

The Cosmic Evolution Early Release Science (CEERS) Survey

PI: Steven Finkelstein (UT Austin) Co-I’s: Mark Dickinson (NOAO), Harry Ferguson (STScI), Andrea Grazian (Rome), Norman Grogin (STScI), Jeyhan Kartaltepe (RIT), Lisa Kewley (ANU), Dale Kocevski (Colby), Anton Koekemoer (STScI), Jennifer Lotz (STScI), Casey Papovich (Texas A&M), Laura Pentericci (Rome), Pablo Perez- Gonzalez (Madrid), Nor Pirzkal (STScI), Swara Ravindranath (STScI), Rachel Somerville (Rutgers), Jon Trump (UConn) & Steve Wilkins (Sussex) Full CEERS team: 105 scientists over 10 countries, including 28 institutions

CEERS Observing Plan

• Primary Field: EGS
• Image shows our reconfigured
• bservations assuming a Spring

2019 launch, and observations in Dec 2019.

• 6 pointings: NIRSpec prime with

NIRCam parallel

• Imaging in 5-6 filters (1.2-4.5 μm).
• R~1000 spectroscopy in all six

pointings, R~100 in four pointings.

• 4 pointings: MIRI prime w/ NIRCam in

parallel

• MIRI: 2 pointings deep F560W &

F770W, 2 pointings shallower obs

• ut to 21 μm.
• 4 pointings: NIRCam grism prime

(F356W)

APT file is available by searching program #1345 at: https://jwst.stsci.edu/observing-programs/program-information

CEERS: Primary Science Goals

• Numbers shown are those

expected in CEERS at M <

• 19.5 at z~10 and 11.5 for

two competing models. 6±2 33±8 13±4 1±1

Figur number density at M< -19.5. Lines denote individual models, while the shaded r the r and gas density within the semi- analytic model of Y (2017, in pr Σ Σ dependence Σ Σ While models ar with data at z<8, they diver higher r distinguish between these models at ~3σ two r

1) CEERS should detect ~5-50 galaxies at z > 10, distinguishing between models which assume different star-forming efficiencies, in addition to finding high-priority targets for Cycle 2. 2) CEERS NIRSpec and NIRCam grism will detect numerous lines out to z~10, allowing spectroscopic confirmation and measurement of key physical properties, including ionization parameter, metallicity, and AGN presence.

Grism sims by Nor Pirzkal

3) CEERS will unveil high-resolution rest-optical morphologies for modestly-high redshift galaxies, and high-resolution imaging in the PAH/hot-dust continuum for galaxies at moderate redshifts.

z~2

z~1.5

Example z~9 Observation

Deliverables

Build and release simulated CEERS datasets. Make updated HST mosaics & catalogs. Also will communicate to community, including blog detailing our interaction with the data (simulated and real), and “CEERS briefings” Pre-Launch

v0.5 image mosaics for NIRCam and MIRI

• v0.5 reduced 2D and 1D spectra for NIRSpec and NIRCam grism

3 months post-data acquisition (by Cycle 2 Call)

v1 image mosaics and 2D and 1D spectra PSF-matched photometry catalog HST+NIRCam, MIRI v1 Spectroscopic catalog (line fluxes and spectroscopic redshifts) Release sample of z > 9 galaxy candidates

6 months post-data acquisition (by Cycle 2 deadline) 12 months post- data acquisition

v2 image mosaics and 2D and 1D spectra Publish multi-wavelength catalog, including photo-z, M*, SFR v2 Spectroscopic catalog (line fluxes and spectroscopic redshifts) F200W morphology catalog Publication of slit-loss analysis

C O N C L U S I O N S

• Lyα is beginning to fulfill its “destiny” as a tracer of the

evolution of reionization, but a robust baseline sample of

• bjects at lower redshifts is needed to help the interpretation.
• HETDEX is well on its way, and will provide very large samples
• f LAEs which can be used to create such a baseline.
• Early HETDEX data show signs of an interesting population
• f high-EW LAEs
• JWST observations (like CEERS) can be used to understand

the physical mechanisms promoting this emission.