Submm galaxies and EROs: Submm galaxies and EROs: Expectations for FMOS in the Expectations for FMOS in the light of OHS observationslight of OHS observations

Chris Simpson (University of Chris Simpson (University of Durham)Durham)

Further reading…Further reading…

SMGs: Simpson, Dunlop, Eales, Ivison, SMGs: Simpson, Dunlop, Eales, Ivison, Scott, Lilly, & WebbScott, Lilly, & Webb

EROs: Cotter, Simpson, & BoltonEROs: Cotter, Simpson, & Bolton

Both papers in advanced draft stage and Both papers in advanced draft stage and soon to be submitted to MNRAS.soon to be submitted to MNRAS.

Why FMOS is better than OHSWhy FMOS is better than OHS

MultiplexingMultiplexing Can observe targets for an entire night (or Can observe targets for an entire night (or

longer)longer)

Higher spectral resolutionHigher spectral resolution More sensitive to emission and absorption More sensitive to emission and absorption

lineslines

More extensive wavelength coverageMore extensive wavelength coverage Increased probability of measuring redshifts or Increased probability of measuring redshifts or

useful diagnosticsuseful diagnostics

Increased throughputIncreased throughput Better sensitivityBetter sensitivity

SMGs: introductionSMGs: introduction

The extragalactic submillimetre background The extragalactic submillimetre background has been resolved into submillimetre has been resolved into submillimetre galaxies (SMGs) which appear to be dusty galaxies (SMGs) which appear to be dusty vigorous star-forming galaxies.vigorous star-forming galaxies.

Half the total extragalactic background is in Half the total extragalactic background is in the submm, while SMGs make up more than the submm, while SMGs make up more than half the extragalactic submm backgroundhalf the extragalactic submm background

>25% of all stars since the Big Bang have >25% of all stars since the Big Bang have formed in SMGs.formed in SMGs.

SMGs: scientific motivationSMGs: scientific motivation

The strong k-correction for SMGs biases an The strong k-correction for SMGs biases an 850850μμm flux-limited sample to high redshifts.m flux-limited sample to high redshifts.

if 25% of SMGs have z<2 (Chapman et al. if 25% of SMGs have z<2 (Chapman et al. 2003), then ~70% of stars formed at z<2.2003), then ~70% of stars formed at z<2.

FMOS studies of SMGs are motivated toFMOS studies of SMGs are motivated to measure redshifts where optical spectroscopy measure redshifts where optical spectroscopy

failsfails make alternative measurements of the SFRsmake alternative measurements of the SFRs

SMGs: number densitySMGs: number density

SMGs have a sky SMGs have a sky density of density of 200/FOV with a 200/FOV with a flux of Sflux of S850850>4mJy>4mJy

~10~10σσconfusionconfusion

SCUBA-2 (2007) SCUBA-2 (2007) will cover ~3 will cover ~3 degdeg22 per week to per week to this limit.this limit.

Borys et al. (2003)

Map production and source extraction Map production and source extraction by Susan Scott for the SHADES by Susan Scott for the SHADES consortiumconsortium

SMGs: redshift distributionSMGs: redshift distribution

Chapman et al. Chapman et al. (2003) find a (2003) find a broad redshift broad redshift distribution for distribution for SMGs, with a SMGs, with a median redshift median redshift ‹z›=2.4.‹z›=2.4.

The The spectroscopic spectroscopic completeness is completeness is uncertain.uncertain.

SMGs: star formation ratesSMGs: star formation rates

Galaxies with SGalaxies with S850850~8mJy have SFRs ~8mJy have SFRs ~1000M~1000MΘΘ/yr./yr.

This is a sensitive function of the assumed This is a sensitive function of the assumed dust temperature (Tdust temperature (T66 for z<3). for z<3).

Optical spectroscopy gives ~10-20MOptical spectroscopy gives ~10-20MΘΘ/yr on /yr on average.average.

SMGs: May 2002 OHS SMGs: May 2002 OHS observationsobservations

Five nights (19-23 May 2003) shared 60-40 Five nights (19-23 May 2003) shared 60-40 with a second proposal.with a second proposal.

Several hours lost to weather and technical Several hours lost to weather and technical problems, so seven targets were observedproblems, so seven targets were observed

selected from the 8mJy survey and CUDSS 14h selected from the 8mJy survey and CUDSS 14h fieldfield

chosen to be too faint for optical spectrographschosen to be too faint for optical spectrographs

Each target was observed for 8x1000s Each target was observed for 8x1000s exposures with a 1” slit in ~0.6” seeing.exposures with a 1” slit in ~0.6” seeing.

SMGs: summary of resultsSMGs: summary of results

Reliable redshifts were obtained for ?/7 targets.Reliable redshifts were obtained for ?/7 targets.Reliable redshifts were obtained for 3/7 targets.Reliable redshifts were obtained for 3/7 targets.

SMGs: LE 850.3 at z=2.120 SMGs: LE 850.3 at z=2.120

[OII]/H[OII]/Hββ~3 (predicted) so the absence of H-~3 (predicted) so the absence of H-band lines is not unexpected. The continuum band lines is not unexpected. The continuum break is well-fit by a 250 Myr starburst.break is well-fit by a 250 Myr starburst.

[OII] Hβ [OIII]Balmer jump

SMGs: N2 850.2 at z=2.453SMGs: N2 850.2 at z=2.453

The OHS redshift of z=2.453±0.006 agrees The OHS redshift of z=2.453±0.006 agrees well with the optical redshift of z=2.443 and well with the optical redshift of z=2.443 and CO redshift z=2.442.CO redshift z=2.442.

[OII] Hβ [OIII]

SMGs: N2 850.12 at z=2.425SMGs: N2 850.12 at z=2.425

[OII] is expected in the least sensitive region [OII] is expected in the least sensitive region of the spectrum, so the absence of a formal of the spectrum, so the absence of a formal detection is not inconsistent with [OII]/Hdetection is not inconsistent with [OII]/Hββ~3.~3.

[OII] [OIII]Hβ

SMGs: simulated FMOS SMGs: simulated FMOS spectrum of ELAIS N2 850.12spectrum of ELAIS N2 850.12

A simulated 7-hour spectrum produces lines and A simulated 7-hour spectrum produces lines and continuum with sufficient S/N to do science!continuum with sufficient S/N to do science!

The vast The vast majority of majority of SMGs should SMGs should provide provide redshifts with redshifts with FMOS.FMOS.

SMGs: the IR redshift desertSMGs: the IR redshift desert

Our 3Our 3σσ line flux sensitivies correspond to line flux sensitivies correspond to star formation rates ~10Mstar formation rates ~10MΘΘ/yr (cf. Ly/yr (cf. Lyαα fluxes).fluxes).At 2.6<z<3.0:At 2.6<z<3.0: HHββ is between H & K is between H & K [OII] is between J & [OII] is between J &

HH HHαα is beyond K is beyond K

This is the IR This is the IR “redshift desert”.“redshift desert”.

EROs: introductionEROs: introduction

Extremely Red Objects (EROs) have red Extremely Red Objects (EROs) have red optical- infrared colours:optical- infrared colours:

R-K>6, R-K>5, I-K>4, I-H>3, etc.R-K>6, R-K>5, I-K>4, I-H>3, etc.

Such colours can be caused by either an old Such colours can be caused by either an old stellar population, or a younger, dust-stellar population, or a younger, dust-reddened population at high redshift (z>1).reddened population at high redshift (z>1).

EROs: scientific motivationEROs: scientific motivation

The “passive” EROs suggest an early epoch The “passive” EROs suggest an early epoch of galaxy assembly and an even earlier of galaxy assembly and an even earlier epoch of star formation.epoch of star formation.

The starbursting EROs are sites of extreme The starbursting EROs are sites of extreme star formation at moderate redshiftsstar formation at moderate redshifts

identification with submm sources below identification with submm sources below SCUBA confusion limit?SCUBA confusion limit?

sites of major mergers?sites of major mergers?

EROs: number densityEROs: number density

A surface density A surface density of 200/FMOS FOV of 200/FMOS FOV corresponds to corresponds to K~19-20, K~19-20, depending on depending on one’s definition of one’s definition of ERO.ERO.

around the around the UKIDSS DXS UKIDSS DXS limit.limit.

Yan & Thompson (2003)

EROs: photometric EROs: photometric classificationclassification

Pozzetti & Pozzetti & Mannucci (2000) Mannucci (2000) suggest that suggest that ellipticals and ellipticals and dusty starbursts dusty starbursts can be can be distinguished in a distinguished in a colour-colour colour-colour diagram.diagram.

EROs: photometric EROs: photometric classificationclassification

Mannucci et al. (2002) find approximately Mannucci et al. (2002) find approximately equal numbers of Es and SBs.equal numbers of Es and SBs.

The distribution of galaxies is not bimodal, The distribution of galaxies is not bimodal, and photometric uncertainties are large.and photometric uncertainties are large.

EROs: morphological EROs: morphological classificationclassification

Yan & Thompson (2003) find more disks Yan & Thompson (2003) find more disks than spheroids from their analysis of than spheroids from their analysis of HST/WFPC2 F814W images.HST/WFPC2 F814W images.

EROs: spectroscopic EROs: spectroscopic classificationclassification

Cimatti et al. (2002) took optical spectra of Cimatti et al. (2002) took optical spectra of EROs from the K20 sample and found EROs from the K20 sample and found roughly equal numbers of Es and SBs.roughly equal numbers of Es and SBs.

K20 galaxies have R-K>5 and the average K20 galaxies have R-K>5 and the average colour is R-K=5.2. colour is R-K=5.2.

EROs: Jun 2001 OHS EROs: Jun 2001 OHS observationsobservations

One night (11 June 2001), hampered by poor One night (11 June 2001), hampered by poor seeing and the telescope oscillation problem.seeing and the telescope oscillation problem.

Three targets were observed in the field of Three targets were observed in the field of the wide-angle quasar pair PC 1643+4631A,B the wide-angle quasar pair PC 1643+4631A,B (which includes HR10 at z=1.44).(which includes HR10 at z=1.44).

These were selected to have R-K>5.5 from These were selected to have R-K>5.5 from the optical/infrared data of T. Haynes et al. the optical/infrared data of T. Haynes et al. (2002).(2002).

EROs: summary of resultsEROs: summary of results

Two objects displayed featureless continua Two objects displayed featureless continua with no evidence of spectral breaks, while with no evidence of spectral breaks, while one (object #09 in the Haynes et al. one (object #09 in the Haynes et al. catalogue) showed a prominent emission catalogue) showed a prominent emission line at 15373Å.line at 15373Å.

ERO J164504.5+462551: ERO J164504.5+462551: spectroscopic propertiesspectroscopic properties

The emission line is identified as HThe emission line is identified as Hαα at at z=1.34.z=1.34.

[OII] at z=3.12 is ruled out from the absence [OII] at z=3.12 is ruled out from the absence of a continuum break and the extreme of a continuum break and the extreme continuum luminosity it would imply.continuum luminosity it would imply.

The line is unresolved, implying little [NII] The line is unresolved, implying little [NII] emission.emission.

The emission is powered by star formation, The emission is powered by star formation, rather than an AGN.rather than an AGN.

The inferred SFR is ~20 MThe inferred SFR is ~20 MΘΘ/yr./yr.

ERO J164504.5+462551: ERO J164504.5+462551: morphological propertiesmorphological properties

TH09 looks like a TH09 looks like a bulge-dominated bulge-dominated passive galaxy.passive galaxy.

ERO J164504.5+462551: ERO J164504.5+462551: photometric propertiesphotometric properties

The near-infrared photometry of TH09 is not The near-infrared photometry of TH09 is not very precise, but the object lies close to the very precise, but the object lies close to the line which separates Es from SBs.line which separates Es from SBs.

TH09 has TH09 has MMBB=-21.0=-21.0

~M*~M*

ERO J164504.5+462551: SEDERO J164504.5+462551: SED

The optical-IR SED can be fit with a The optical-IR SED can be fit with a combination of old (5Gyr) and young, combination of old (5Gyr) and young, reddened stellar populations.reddened stellar populations.

The young The young pop has Av~3 pop has Av~3 and an SFR of and an SFR of ~80M~80MΘΘ/yr, /yr, consistent consistent with the Hwith the Hαα flux and 8-flux and 8-GHz radio flux GHz radio flux limit.limit.

A 7-hour observation of this ERO would detect HA 7-hour observation of this ERO would detect Hββ

EROs: FMOS simulated EROs: FMOS simulated spectrum of ERO spectrum of ERO J164504.5+462551J164504.5+462551

get reddening get reddening from Balmer from Balmer decrementdecrement

It would resolve It would resolve HHαα and [N II] and [N II] importance of importance of

AGN contributionAGN contribution

SummarySummary

EROs and SMGs both have number EROs and SMGs both have number densities appropriate for FMOS densities appropriate for FMOS observations.observations.

EROs: K < 20EROs: K < 20 SMGs: SSMGs: S850850 > 5 mJy > 5 mJy

Single-night FMOS observations should be Single-night FMOS observations should be sensitive enough tosensitive enough to

measure redshifts and accurate line fluxesmeasure redshifts and accurate line fluxes study the stellar continuumstudy the stellar continuum