The Sydney-AAO Multi-object Integral field spectrograph (SAMI) (1112.3367v1)

Abstract: We demonstrate a novel technology that combines the power of the multi-object spectrograph with the spatial multiplex advantage of an integral field spectrograph (IFS). The Sydney-AAO Multi-object IFS (SAMI) is a prototype wide-field system at the Anglo-Australian Telescope (AAT) that allows 13 imaging fibre bundles ("hexabundles") to be deployed over a 1-degree diameter field of view. Each hexabundle comprises 61 lightly-fused multimode fibres with reduced cladding and yields a 75 percent filling factor. Each fibre core diameter subtends 1.6 arcseconds on the sky and each hexabundle has a field of view of 15 arcseconds diameter. The fibres are fed to the flexible AAOmega double-beam spectrograph, which can be used at a range of spectral resolutions (R=lambda/delta(lambda) ~ 1700-13000) over the optical spectrum (3700-9500A). We present the first spectroscopic results obtained with SAMI for a sample of galaxies at z~0.05. We discuss the prospects of implementing hexabundles at a much higher multiplex over wider fields of view in order to carry out spatially--resolved spectroscopic surveys of 10^4 to 10^5 galaxies.

• The paper presents SAMI as an innovative instrument that combines multi-object spectroscopy with hexabundle technology to enable comprehensive spatially-resolved galaxy surveys.
• It details the use of 61-fiber hexabundles and the AAOmega spectrograph to achieve a 1-degree field of view and capture spectra from 3700 to 9500 Å with varying resolutions.
• The instrument’s capabilities promise transformative advancements in galaxy evolution studies by supporting surveys of up to 100,000 galaxies with enhanced data richness.

Overview of the Sydney-AAO Multi-object Integral Field Spectrograph (SAMI)

The paper outlines the development and capabilities of the Sydney-AAO Multi-object Integral Field Spectrograph (SAMI), a pioneering instrument designed for the Anglo-Australian Telescope (AAT). SAMI introduces novel technology by combining features of a multi-object spectrograph with integral field spectroscopy advantages. This instrument allows simultaneous observation of 13 proxies using hexabundle technology, paving the way for large-scale spatially-resolved spectroscopic surveys of galaxies.

Technical Implementation

SAMI represents a technological advancement, integrating hexabundles—a type of optical fibre bundle without lenslets—into its design. Each hexabundle consists of 61 fibers with a reduced cladding layer to enhance flux collection efficiency, achieving a filling factor of 75%. Hexabundles enable SAMI to spatially sample spectra across a significant field of view (FOV), providing a 1-degree FOV at the AAT’s prime focus. The fibers are routed to the AAOmega double-beam spectrograph, which operates over a spectrum range of 3700-9500 Å with resolutions from R=1700 to R=13000.

Scientific Goals

The primary scientific rationale behind SAMI is to elucidate complex processes in galaxy formation and evolution. By capturing spatially-resolved spectroscopy of galaxies, SAMI aims to address key questions about galaxy dynamics, star formation history, black hole accretion rates, and feedback processes. It delivers crucial insights into not only galaxy structure and kinematics but also emission line diagnostics across diverse galactic environments.

Observational Performance

The instrument has demonstrated functionality through initial observations of galaxies at redshift z≈0.05, achieving a throughput consistent with expectations from laboratory measurements. Although current fiber throughput is suboptimal, improvements through fiber replacement are anticipated, particularly for blue wavelengths where losses are more pronounced.

Implications and Future Directions

SAMI heralds a transformative phase for galaxy surveys by shifting from single-fiber toward multiplexed integral field spectroscopy. This capability significantly enhances data richness, offering insights unavailable from traditional single-aperture spectroscopy. The successful deployment of SAMI sets the stage for comprehensive surveys involving 10,000-100,000 galaxies, contributing substantially to understanding galaxy formation dynamics.

Future endeavors could involve expanding the SAMI concept to larger field of view adaptations on new and existing telescopes, necessitating parallel advancements in spectrograph throughput to maintain data processing efficiencies with increasing instrument capacity. Such expansions will benefit from the continued development and implementation of technologies like hexabundles, which provide high-density spatial sampling while maintaining collection efficiency.

Conclusion

SAMI exemplifies a successful implementation of astrophotonic advancements and its potential for expanding our understanding of galactic processes. The prospects for more detailed and expansive spectroscopic surveys will likely yield a deeper comprehension of the complex physics governing galaxy evolution, marking an important epoch in spectrographic instrumentation for astronomy.