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Galaxy NGC 474
Science & Technology

Needle in a Haystack: Planetary Nebulae Detected in Distant Galaxies

The ring galaxy NGC 474 at a distance of about 110 million gentle years. The ring construction was fashioned by merging processes of colliding galaxies. Credit score: DES/DOE/Fermilab/NCSA & CTIO/NOIRLab/NSF/AURA

Utilizing information from the MUSE instrument, researchers on the Leibniz Institute for Astrophysics Potsdam (AIP) succeeded in detecting extraordinarily faint planetary nebulae in distant galaxies. The tactic used, a filter algorithm in picture information processing, opens up new prospects for cosmic distance measurement – and thus additionally for figuring out the Hubble fixed.

Planetary nebulae are recognized in the neighborhood of the Solar as colourful objects that seem on the finish of a star’s life because it evolves from the pink large to white dwarf stage: when the star has used up its gasoline for nuclear fusion, it blows off its gasoline envelope into interstellar area, contracts, turns into extraordinarily sizzling, and excites the increasing gasoline envelope to glow. Not like the continual spectrum of the star, the ions of sure components in this gasoline envelope, comparable to hydrogen, oxygen, helium, and neon, emit gentle solely at sure wavelengths. Particular optical filters tuned to those wavelengths could make the faint nebulae seen. The closest object of this type in our Milky Means is the Helix Nebula, 650 gentle years away.

The planetary nebula NGC 7294 (“Helix Nebula”), an object in the neighborhood of the Solar. Credit score: NASA, NOAO, ESA, the Hubble Helix Nebula Workforce, M. Meixner (STScI), and T.A. Rector (NRAO)

As the space of a planetary nebula will increase, the obvious diameter in a picture shrinks, and the built-in obvious brightness decreases with the sq. of the space. In our neighboring galaxy, the Andromeda Galaxy, at a distance virtually 4000 occasions larger, the Helix Nebula would solely be seen as a dot, and its obvious brightness can be virtually 15 million occasions fainter. With fashionable massive telescopes and lengthy publicity occasions, such objects can nonetheless be imaged and measured utilizing optical filters or imaging spectroscopy.

Martin Roth, first creator of the brand new examine and head of the innoFSPEC division at AIP: “Utilizing the PMAS instrument developed at AIP, we succeeded in doing this for the primary time with integral subject spectroscopy for a handful of planetary nebulae in the Andromeda Galaxy in 2001 to 2002 on the three.5m telescope of the Calar Alto Observatory. Nevertheless, the comparatively small PMAS field-of-view didn’t enable but to research a bigger pattern of objects.”

It took a good 20 years to develop these first experiments additional utilizing a extra highly effective instrument with a greater than 50 occasions bigger field-of-view on a a lot bigger telescope. MUSE on the Very Massive Telescope in Chile was developed primarily for the invention of extraordinarily faint objects on the fringe of the universe at present observable to us – and has produced spectacular results for this objective for the reason that first observations. It’s exactly this property that additionally comes into play in the detection of extraordinarily faint PN in a distant galaxy.

MUSE picture information in the 2 marked fields in the above picture of the ring construction of NGC 474. Left: Picture in the continuum with the band of unresolved stars in addition to globular clusters marked by circles. Proper: filtered picture in the redshifted oxygen emission line, from which the planetary nebulae emerge as level sources from the noise. The artifacts created by instrumental results have utterly disappeared. Credit score: AIP/M. Roth

The galaxy NGC 474 is a notably positive instance of a galaxy that, by means of collision with different, smaller galaxies, has fashioned a conspicuous ring construction from the celebrities scattered by gravitational results. It lies roughly 110 million gentle years away, which is about 170,000 occasions additional than the Helix Nebula. The obvious brightness of a planetary nebula in this galaxy is due to this fact virtually 30 billion occasions decrease than that of the Helix Nebula and is in the vary of cosmologically fascinating galaxies for which the workforce designed the MUSE instrument.

A workforce of researchers on the AIP, along with colleagues from the USA, has developed a technique for utilizing MUSE to isolate and exactly measure the extraordinarily faint alerts of planetary nebulae in distant galaxies with excessive sensitivity. A very efficient filter algorithm in picture information processing performs an necessary function right here. For the ring galaxy NGC 474, ESO archive information had been out there, based mostly on two very deep MUSE exposures with 5 hours of statement time every. The results of the information processing: after making use of the filter algorithm, a complete of 15 extraordinarily faint planetary nebulae grew to become seen.

This extremely delicate process opens up a new technique for distance measurement that’s appropriate for contributing to the answer of the at present mentioned discrepancy in the dedication of the Hubble fixed. Planetary nebulae have the property that, bodily, a sure most luminosity can’t be exceeded. The distribution perform of the luminosities of a pattern in a galaxy, i.e. the luminosity perform of planetary nebulae (PNLF), breaks off on the vibrant finish. This property is that of a customary candle, which can be utilized to calculate a distance by statistical strategies. The PNLF technique has been developed already in 1989 by workforce members George Jacoby (NSF’s NOIRLab) and Robin Ciardullo (Penn State College). It has been efficiently utilized to greater than 50 galaxies over the previous 30 years, however was restricted by the filter measurements used up to now. Galaxies with distances larger than that of the Virgo or Fornax clusters had been past the vary.

The examine, now revealed in The Astrophysical Journal, exhibits that MUSE can obtain greater than twice the vary, permitting an impartial measurement of the Hubble fixed.

Reference: “Towards Precision Cosmology with Improved PNLF Distances Utilizing VLT-MUSEI. Methodology and Exams” by Martin M. Roth, George H. Jacoby, Robin Ciardullo, Brian D. Davis, Owen Chase and Peter M. Weilbacher, 22 July 2021, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ac02ca

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