The newest mapmaking effort of the long-running Sloan Digital Sky Survey (SDSS) has begun.
The Local Volume Mapper (LVM) Instrument has made its first observations, also known as “first light.” LVM is one of the three mappers that make up the fifth phase of the SDSS’s ambitious all-sky, multi-epoch spectroscopic survey. This new instrument will create a spectroscopic map of the Milky Way Galaxy and other nearby galaxies.
“This is not just a new instrument — it is an entirely new observatory that we created as part of SDSS,” said Juna Kollmeier, director of the fifth and current phase of the SDSS and director of the Faculty of Arts & Science’s Canadian Institute for Theoretical Astrophysics (CITA). “Integral field spectroscopy is part of the rugged frontier of 21st century astronomical observations. I am awed and humbled by the achievements of this talented and dedicated international team!”
LVM is the first spectroscopic survey to cover such a large area of the sky in a homogenous way. What makes it new is its approach to mapping the sky. While previous surveys have focused on individual stars, quasars and galaxies, LVM will observe the interstellar medium (ISM) — the gas and dust that fills the space between stars. The survey will examine this gas and how it interacts with the stars not just in the Milky Way Galaxy, but also in our companion galaxies, the Magellanic Clouds, and several other nearby galaxies in what is known as the Local Group.
“The LVM is exciting because it will give an unprecedented unbiased view of the ISM in which the bright nebulae are immersed,” says CITA’s Peter Martin, who has studied the ISM throughout his career. “This will show the interconnections between signposts of star formation — shocks, outflows and protostellar knots. It will also show the impact of stellar death that returns material to the ISM, for example, planetary nebulae and supernova remnants.”
The LVM telescopes work like a fly’s eye, in which thousands of individual small lenses separate the light from little patches of sky to collect their spectra, which are measurements of the amount of light that the gas and stars emit at different frequencies. Researchers turn these measurements into a graph that they can read to decode information about the source. This fly’s eye approach allows LVM to take spectra of thousands of neighboring patches over an entire area of the sky at once.
“We have always looked at individual objects in the Milky Way Galaxy,” says Niv Drory of the University of Texas at Austin and program head of the LVM project. “Now, we look at everything. No gaps, no selection effects — we observe the whole sky.”
The first step toward completing this ambitious all-sky mapping project has begun, with the first science observations of the new Local Volume Mapper Instrument (LVM-I), located at Las Campanas Observatory high in the Atacama Desert of northern Chile. The innovative instrument and telescope design will allow astronomers to use the Milky Way Galaxy as an astrophysical laboratory to understand how stars form and inject energy, momentum and chemical elements into their local surroundings. This energy cycle is essential for understanding the physics of galaxy formation.
LVM-I consists of four custom-built telescopes. One telescope performs science observations, while the other three are devoted to real-time calibration observations. A massive fibre bundle, consisting of 2,000 optical fibres, carries the visible light from the telescopes to three spectrographs where the light is separated into different frequencies and analyzed.
“LVM is the first application of this technique to the entire Milky Way Galaxy and is the first step towards a spectroscopic survey of the entire sky,” said Evelyn Johnston, the survey operations scientist for LVM, of University of Diego Portales in Santiago, Chile. “We will be able to resolve star forming regions less than one light-year across, giving us unprecedented detail of these important structures.”
“This comprehensive view of these nearby systems is only possible with a unified survey program such as SDSS,” said Kathryn Kreckel of Heidelberg University, the survey scientist for Local Volume Mapper.
Now that the facility has been built, and science commissioning has begun, the next step is to begin full science operations. Observations will continue until 2027, covering the Milky Way Galaxy and several other Local Group galaxies.
The result will be a dense spectral map that can be compared to our current theories of galaxy formation and evolution to test how energy and chemicals are cycled through the interstellar medium through stars. This process of star formation and feedback is critical to understanding galaxies across all cosmic epochs. The local volume mapper will provide an essential local laboratory to unravel this process.
With files from Johns Hopkins University.