Using an artificial neural network to classify multicomponent emission lines with integral field spectroscopy from SAMI and S7

Hampton, Elise; Medling, Anne M.; Groves, Brent; Kewley, Lisa J.; Dopita, Michael A.; Davies, R. L.; Ho, I-Ting; Kaasinen, Melanie; Leslie, S. K.; Sharp, Robert; Sweet, Sarah M.; Thomas, Amberyn; Allen, J. T.; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Croom, S. M.; Goodwin, Michael; Green, A.; Konstantantopoulos, I. S.; Lawrence, Jon; López-Sánchez, Á. R.; Lorente, Nuria P. F.; McElroy, Rebecca; Owers, Matt S.; Richards, Samuel N.; Shastri, P.

doi:10.1093/mnras/stx1413

Cited by 28 publications

(23 citation statements)

References 37 publications

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“…We determined the number of components appropriate for each spaxel using an artificial neural net (LZComp; Hampton et al 2017), trained by five SAMI astronomers. We adopted the results from LZComp with the additional stipulation that the Hα emission line must have a signal-to-noise ratio of at least 5 in each component; if it did not, the number of components for that spaxel was reduced until the stipulation was met (or until only one component remained).…”

Section: Emission Line Fitsmentioning

confidence: 99%

The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

Medling

Cortese

Croom

et al. 2018

Monthly Notices of the Royal Astronomical Society

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119

103

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We present the ∼800 star formation rate maps for the SAMI Galaxy Survey based on Hα emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1. We mask out spaxels contaminated by non-stellar emission using the [O III]/Hβ, [N II]/Hα, [S II]/Hα, and [O I]/Hα line ratios. Using these maps, we examine the global and resolved star-forming main sequences of SAMI galaxies as a function of morphology, environmental density, and stellar mass. Galaxies further below the star-forming main sequence are more likely to have flatter star formation profiles. Early-type galaxies split into two populations with similar stellar masses and central stellar mass surface densities. The main sequence population has centrally-concentrated star formation similar to late-type galaxies, while galaxies >3σ below the main sequence show significantly reduced star formation most strikingly in the nuclear regions. The split populations support a two-step quenching mechanism, wherein halo mass first cuts off the gas supply and remaining gas continues to form stars until the local stellar mass surface density can stabilize the reduced remaining fuel against further star formation. Across all morphologies, galaxies in denser environments show a decreased specific star formation rate from the outside in, supporting an environmental cause for quenching, such as ram-pressure stripping or galaxy interactions.

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Section: Emission Line Fitsmentioning

confidence: 99%

The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

Medling

Cortese

Croom

et al. 2018

Monthly Notices of the Royal Astronomical Society

Self Cite

119

103

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“…Each spaxel is fit 3 times using lzifu to obtain one, two and three component fits to each emission line. The number of components in the multicomponent fits are determined using an artificial neural network trained by astronomers (for full details on the neural network, and precision success with SAMI data, see Hampton et al 2017).…”

Section: Emission-line Fittingmentioning

confidence: 99%

The SAMI Galaxy Survey: Data Release Two with absorption-line physics value-added products

Scott

Sande

Croom

et al. 2018

Monthly Notices of the Royal Astronomical Society

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105

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We present the second major release of data from the SAMI Galaxy Survey. Data Release Two includes data for 1559 galaxies, about 50% of the full survey. Galaxies included have a redshift range 0.004 < z < 0.113 and a large stellar mass range 7.5 < log(M /M ) < 11.6. The core data for each galaxy consist of two primary spectral cubes covering the blue and red optical wavelength ranges. For each primary cube we also provide three spatially binned spectral cubes and a set of standardised aperture spectra. For each core data product we provide a set of value-added data products. This includes all emission line value-added products from Data Release One, expanded to the larger sample. In addition we include stellar kinematic and stellar population value-added products derived from absorption line measurements. The data are provided online through Australian Astronomical Optics' Data Central. We illustrate the potential of this release by presenting the distribution of ∼ 350, 000 stellar velocity dispersion measurements from individual spaxels as a function of R/R e , divided in four galaxy mass bins. In the highest stellar mass bin (log(M /M ) > 11), the velocity dispersion strongly increases towards the centre, whereas below log(M /M ) < 10 we find no evidence for a clear increase in the central velocity dispersion. This suggests a transition mass around log(M /M ) ∼ 10 for galaxies with or without a dispersion-dominated bulge.

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“…It would also be interesting to explore the extent to which the recent generation of integral field spectroscopic surveys may be able to bridge the two, applying techniques so far used only for star forming galaxies but instead looking at passive systems with some residual star formation. With spatially resolved spectra, any AGN contributions may be identified and excluded to isolate star formation signatures in otherwise passive galaxies (e.g., Hampton et al 2017;Medling et al 2018), allowing the Kennicutt (1983) and related approaches to be applied.…”

Section: Passive Galaxiesmentioning

confidence: 99%

The Dawes Review 8: Measuring the Stellar Initial Mass Function

Hopkins

2018

Publ. Astron. Soc. Aust.

106

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The birth of stars and the formation of galaxies are cornerstones of modern astrophysics. While much is known about how galaxies globally and their stars individually form and evolve, one fundamental property that affects both remains elusive. This is problematic because this key property, the birth mass distribution of stars, referred to as the stellar initial mass function (IMF), is a key tracer of the physics of star formation that underpins almost all of the unknowns in galaxy and stellar evolution. It is perhaps the greatest source of systematic uncertainty in star and galaxy evolution. A star's initial mass determines its luminosity, lifetime, and eventual return of material enriched by nuclear fusion back to the interstellar medium to be incorporated in later generations of stars. The distribution of stellar masses created in star formation events therefore determines the evolution of galaxies over cosmic time, and accurately measuring it is crucial. The past decade has seen a growing number and variety of methods for measuring or inferring the shape of the IMF, along with progressively more detailed simulations, paralleled by refinements in the way the concept of the IMF is applied or conceptualised on different physical scales. This range of approaches and evolving definitions of the quantity being measured has in turn led to conflicting conclusions regarding whether or not the IMF is universal. Here I review and compare the growing wealth of approaches to our understanding of this fundamental property that defines so much of astrophysics. I summarise the observational measurements from stellar analyses, extragalactic studies and cosmic constraints, and highlight the importance of considering potential IMF variations, reinforcing the need for measurements to quantify their scope and uncertainties carefully, in order for this field to progress. I present a new framework to aid the discussion of the IMF and promote clarity in the further development of this fundamental field.

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Using an artificial neural network to classify multicomponent emission lines with integral field spectroscopy from SAMI and S7

Cited by 28 publications

References 37 publications

The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

The SAMI Galaxy Survey: Data Release Two with absorption-line physics value-added products

The Dawes Review 8: Measuring the Stellar Initial Mass Function

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