Spectral Synthesis via Mean Field approach to Independent Component Analysis

Hu, Ning; Su, Shanshan; Kong, Xu

doi:10.1088/1674-4527/16/3/042

Cited by 3 publications

(2 citation statements)

References 57 publications

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“…In general, one needs to disintegrate the emission lines from the underlying stellar continuum, and then measure the fluxes of these lines (Hu et al 2016;Gao et al 2017). For strong emission lines, the subtraction of the stellar continuum has negligible effect on the flux measurements.…”

Section: Spectral Fitting and Emission-line Measurementsmentioning

confidence: 99%

What Determines the Local Metallicity of Galaxies: Global Stellar Mass, Local Stellar Mass Surface Density, or Star Formation Rate?

Gao

Wang

Kong

et al. 2018

ApJ

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The metallicity and its relationship with other galactic properties is a fundamental probe of the evolution of galaxies. In this work, we select about 750,000 star-forming spatial pixels from 1122 blue galaxies in the MaNGA survey to investigate the global stellar mass -local stellar mass surface density -gas-phase metallicity (M * -Σ * -Z ) relation. At a fixed M * , the metallicity increases steeply with increasing Σ * . Similarly, at a fixed Σ * , the metallicity increases strongly with increasing M * at low mass end, while this trend becomes less obvious at high mass end. We find the metallicity to be more strongly correlated to Σ * than to M * . Furthermore, we construct a tight (0.07 dex scatter) M * -Σ * -Z relation, which reduces the scatter in the Σ * -Z relation by about 30% for galaxies with 7.8 < log(M * /M ) < 11.0, while the reduction of scatter is much weaker for high-mass galaxies. This result suggests that, especially for low-mass galaxies, the M * -Σ * -Z relation is largely more fundamental than the M * -Z and Σ * -Z relations, meaning that both M * and Σ * play important roles in shaping the local metallicity. We also find that the local metallicity is probably independent on the local star formation rate surface density at a fixed M * and Σ * . Our results are consistent with the scenario that the local metallicities in galaxies are shaped by the combination of the local stars formed in the history and the metal loss caused by galactic winds.

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Section: Spectral Fitting and Emission-line Measurementsmentioning

confidence: 99%

What Determines the Local Metallicity of Galaxies: Global Stellar Mass, Local Stellar Mass Surface Density, or Star Formation Rate?

Gao

Wang

Kong

et al. 2018

ApJ

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“…We correct the emission-line fluxes for internal dust attenuation using the Balmer decrement measurements, which estimate the dust extinction by inspecting the change of Balmer line ratio, such as Hα/Hβ, from intrinsic value. Generally, the underlying stellar absorption in the Balmer lines should be well determined to obtain a reliable emission line measurement (Hu et al, 2016). In this work, we first subtract the underlying stellar continuum and stellar absorption for each spectrum using the STARLIGHT spectral synthesis code (Cid Fernandes et al, 2005).…”

Section: Dust Attenuation Correctionmentioning

confidence: 99%

A sample of metal-poor galaxies identified from the LAMOST spectral survey

Gao

Lian

Kong

et al. 2017

Res. Astron. Astrophys.

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We present a sample of 48 metal-poor galaxies at z < 0.14 selected from 92,510 galaxies in the LAMOST survey. These galaxies are identified for their detection of the auroral emission line [O III]λ4363 above 3σ level, which allows a direct measurement of the electron temperature and the oxygen abundance. The emission line fluxes are corrected for internal dust extinction using Balmer decrement method. With electron temperature derived from [O III]λλ4959, 5007/[O III]λ4363 and electron density from [S II]λ6731/[S II]λ6717, we obtain the oxygen abundances in our sample which range from 12 + log(O/H) = 7.63 (0.09 Z ⊙ ) to 8.46 (0.6 Z ⊙ ). We find an extremely metal-poor galaxy with 12 + log(O/H) = 7.63 ± 0.01. With multiband photometric data from FUV to NIR and Hα measurements, we also determine the stellar masses and star formation rates, based on the spectral energy distribution fitting and Hα luminosity, respectively. We find that our galaxies have low and intermediate stellar masses with 6.39 ≤ log(M/M ⊙ ) ≤ 9.27, and high star formation rates (SFRs) with −2.18 ≤ log(SFR/M ⊙ yr −1 ) ≤ 1.95. We also find that the metallicities of our galaxies are consistent with the local T e -based mass-metallicity relation, while the scatter is about 0.28 dex. Additionally, assuming the coefficient of α = 0.66, we find most of our galaxies follow the local mass-metallicity-SFR relation, while a scatter about 0.24 dex exists, suggesting the mass-metallicity relation is weakly dependent on SFR for those metal-poor galaxies.

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M101: Spectral Observations of H ii Regions and Their Physical Properties

Wang

Lin

et al. 2018

ApJ

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By using the Hectospec 6.5 m Multiple Mirror Telescope (MMT) and the 2.16 m telescope of National Astronomical Observatories, Chinese Academy of Sciences (NAOC), we obtained 188 high signal-to-noise ratio (S/N) spectra of H ii regions in the nearby galaxy M101, which are the largest spectroscopic sample of H ii regions for this galaxy so far. These spectra cover a wide range of regions on M101, which enables us to analyze two dimensional distributions of its physical properties. The physical parameters are derived from emission lines or stellar continuum, including stellar population age, electron temperature, oxygen abundance and etc. The oxygen abundances are derived using two empirical methods based on O3N2 and R 23 indicators, as well as the direct T e method when [O iii]λ4363 is available. By applying the harmonic decomposition analysis to the velocity field, we obtained line-of-sight rotation velocity of 71 km s −1 and a position angle of 36 degree. The stellar age profile shows an old stellar population in galaxy center and a relative young stellar population in outer regions, suggesting an old bulge and a young disk. Oxygen abundance profile exhibits a clear break at ∼18 kpc, with a gradient of −0.0364 dex kpc −1 in the inner region and −0.00686 dex kpc −1 in the outer region. Our results agree with the "inside-out" disk growth scenario of M101.

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Spectral Synthesis via Mean Field approach to Independent Component Analysis

Cited by 3 publications

References 57 publications

What Determines the Local Metallicity of Galaxies: Global Stellar Mass, Local Stellar Mass Surface Density, or Star Formation Rate?

What Determines the Local Metallicity of Galaxies: Global Stellar Mass, Local Stellar Mass Surface Density, or Star Formation Rate?

A sample of metal-poor galaxies identified from the LAMOST spectral survey

M101: Spectral Observations of H ii Regions and Their Physical Properties

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