Galaxy kinematics with WEAVE high spectral resolution IFU data - - PowerPoint PPT Presentation

Galaxy kinematics with WEAVE high spectral resolution IFU data

Johan H. Knapen Instituto de Astrofísica de Canarias

IFU galaxy kinematics

• Widely available now from many surveys and

instruments, incl. SAURON, MUSE, CALIFA, MaNGA, SAMI

• Usually either limited spectral resolution, or field of

view (or both…)

• WEAVE IFU will give much higher spectral

resolution data over field of view of 1.5 arcmin

Example 1: high-res data to look at gas streaming motions

Hα intensity (left) and velocity field (right) of NGC 1530. From Zurita et al. 2004, A&A, 413, 73 Data from TAURUS at WHT, 19 km/s/pixel

Model of circular motions (left) and residuals after subtracting this from velocity field (right)

• Velocity gradient map (left) shows regions of high shear, which

coincide with location of dust lanes (right)

• Clearly indicates shocks in bar-driven gas
• From Zurita et al. 2004, A&A, 413, 73

Example 2: Inner rotation curve slopes

• Fabry-Perot Hα data with
• res. 8 km/s/pixel (FWHM

19.6 km/s)

• GHaFaS instrument on WHT
• Derive detailed inner rotation

curves of few dozen galaxies

• Could measure inner slopes of rotation curves, and

compare with physical parameters of the galaxies

• Erroz-Ferrer et al. 2016, MNRAS 458, 1119

• µ0 and T-type correlate with inner slope of rotation curve => T-type is

related to the dynamics in the central parts of galaxies, quite plausibly through the radial mass distribution.

• B/T and Mbulge correlate with inner slope => bulges play a role in the

dynamics of the central parts => baryonic mass dominates the dynamics in the inner regions

• From Erroz-Ferrer et al. 2016, MNRAS 458, 1119 (see also Lelli et al.

2013)

WEAVE

• Multi-object spectrograph for

4.2m William Herschel Telescope on La Palma

• Operational early 2019
• 1000 fibres MOS + IFUs
• 2 deg field
• Low and high resolution

modes

• Robotic fibre positioner

WEAVE Characteristics

Telescope, diameter WHT, 4.2m Field of view 2º ∅ Number of fibers 960 (plate A)/940 (plate B) Fiber size 1.3″ Number of small IFUs, size 20 x 11″x12″ (1.3″ spaxels) LIFU size 1.3′x1.5′ (2.6″ spaxels) Low-resolution mode resolution 5750 (3000–7500) Low-resolution mode wavelength coverage (Å) 3660–9590 High-resolution mode resolution 21000 (13000–25000) High-resolution mode wavelength coverage (Å) 4040–4650, 4730–5450 5950–6850

(LIFU half of this) (LIFU half of this)

!

Clockwise: WEAVE dummy top-end being lifted onto WHT; fibre positioner robots; part of spectrograph enclosure; holographic grating

Spectrograph

Two arms split at 595 nm Switchable from low- to high-resolution

WEAVE-APERTIF survey strategy

• Will observe 225 galaxies, each in HR (R=10000) and LR

(R=2500)

• Observing period 2019-2024
• Typical exposure time ~4h per galaxy (ranging from 30min

to 10h, from the brightest objects to the fainter LSBs)

• Wavelength ranges HR (4730-5450Å + 5959-6850Å), LR

(3660-9840Å)

• Main lines:
• HR: Hß, Mgb, Fe5270, Hα
• LR: D4000, Hδ, Hß, Mgb, Fe5270, Hα, NaD, TiO2, CaT
• PI is Jesús Falcón-Barroso (IAC)

Science goals

• Why is there a bimodality in galaxy properties today, so

that there are both star-forming blue galaxies and red, dead galaxies?

• Where does the gas come from that fuels the star

formation in these galaxies?

• How is the star formation shut down?
• How much dark matter do disc galaxies have, and how is

it distributed?

• How do processes like scattering of stars off spiral arms

and bars, radial migration, or accretion of satellites manifest themselves in external disc galaxies?

• Always combine information on gas flows (neutral and

ionised) and stellar kinematics

Sample and data

• Of order 225 nearby galaxies: need <1 kpc scale

and few km/s spectral resolution

• Neutral and ionised gas, and stellar tracers
• APERTIF HI will give neutral gas velocity fields
• WEAVE LIFU will give stellar and ionised gas

kinematics and stellar populations

Participation

• WEAVE is built by consortium of the partners in Isaac

Newton Group of Telescopes (UK, NL, ES), plus participation from F, IT and various smaller parties

• All researchers from UK, NL, ES are free to join, others

may be able to join

• Will operate with policies similar to SDSS, AS-4, in

terms of participation, projects, publication

• All reduced data available internally first, plus annual

public data releases

Summary

• IFUs are powerful instruments to derive gas and

stellar kinematics in galaxies

• Low spectral resolution and limited field of view are

almost always limitations to science output

• WEAVE will deliver high-resolution IFU data of over

200 nearby galaxies, starting 2018/19

• Welcome collaborations and use of the data (subject

to participation rules)