Infrared helium-hydrogen line ratios as a measure of stellar effective temperature

Lumsden, S. L.; Puxley, P. J.; Hoare, M. G.

doi:10.1046/j.1365-8711.2001.03954.x

Cited by 21 publications

(29 citation statements)

References 44 publications

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“…Although the HeI line could be used as a primary indicator of stellar effective temperature, interpreting the emission and the HeI/Brγ ratio without a detailed photoionisation model is still controversial (Doherty et al 1995;Lumsden et al 2001Lumsden et al , 2003. In addition, the HeI transition is also influenced by collisional excitation, and a full photoionisation treatment is not enough to predict the line emission (Shields 1993).…”

Section: Line Ratiosmentioning

confidence: 99%

VLT-SINFONI integral field spectroscopy of low-zluminous and ultraluminous infrared galaxies

López

Colina

Arribas

et al. 2012

A&A

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We present an atlas of a sample of local (z < 0.1) LIRGs (10) and ULIRGs (7) covering the luminosity range log(L IR /L ) = 11.1−12.4. The atlas is based on near-infrared H (1.45−1.85 μm) and K-band (1.95−2.45 μm) VLT-SINFONI integral field spectroscopy (IFS). The atlas presents the ionised, partially ionised, and warm molecular gas two-dimensional flux distributions and kinematics over an FoV of ∼3 × 3 kpc (LIRGs) and ∼12 × 12 kpc (ULIRGs) and with average linear resolutions of ∼0.2 kpc and ∼0.9 kpc, respectively. The different phases of the gas show a wide morphological variety with the nucleus as the brightest Brγ source for ∼33% of the LIRGs and ∼71% of the ULIRGs, whereas all the LIRGs and ULIRGs have their maximum H 2 emission in their nuclear regions. In LIRGs, the ionised gas distribution is dominated by the emission from the star-forming rings or giant HII regions in the spiral arms. The Brγ and [FeII] line at 1.644 μm trace the same structures, although the emission peaks at different locations in some of the objects, and the [FeII] seems to be more extended and diffuse. The ULIRG subsample is at larger distances and contains mainly pre-coalescence interacting systems. Although the peaks of the molecular gas emission and the continuum coincide in ∼71% of the ULIRGs, regions with intense Paα (Brγ) emission tracing luminous star-forming regions located at distances of 2−4 kpc away from the nucleus are also detected, usually associated with secondary nuclei or tidal tails. LIRGs have mean observed (i.e. uncorrected for internal extinction) SFR surface densities of about 0.4 to 0.9 M yr −1 kpc −2 over large areas (4−9 kpc 2 ) with peaks of about 2−2.5 M yr −1 kpc −2 in the smaller regions (0.16 kpc 2 ) associated with the nucleus of the galaxy or the brightest Brγ region. ULIRGs do have similar average SFR surface densities for the integrated emitting regions of ∼0.4 M yr −1 kpc −2 in somewhat larger areas (100−200 kpc 2 ) and for the Paα peak (∼2 M yr −1 kpc −2 in 4 kpc 2 ). The observed gas kinematics in LIRGs is primarily due to rotational motions around the centre of the galaxy, although local deviations associated with radial flows and/or regions of higher velocity dispersions are present. The ionised and molecular gas share the same kinematics (velocity field and velocity dispersion) to first order, showing slight differences in the velocity amplitudes (peak-to-peak) in some cases, whereas the average velocity dispersions are compatible within uncertainties. As expected, the kinematics of the ULIRG subsample is more complex, owing to the interacting nature of the objects of the sample.

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Section: Line Ratiosmentioning

confidence: 99%

VLT-SINFONI integral field spectroscopy of low-zluminous and ultraluminous infrared galaxies

López

Colina

Arribas

et al. 2012

A&A

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“…Line emission from He i is therefore expected to arise predominantly in the vicinity of the most massive (and hence youngest) stars. Interpretation of the He i emission requires detailed photo-ionization models, and quantitative analysis of the temperature of the hottest stars in an H ii region is subject to large uncertainties (Doherty et al 1995;Lumsden et al 2001 qualitatively, however, comparing the He i line strength to that of Brγ provides a handle on the relative ages of the youngest stellar clusters because the hottest stars will vanish fastest. We will use this simple diagnostic in the discussion of age gradients along the rings in Section 4.2.…”

Section: Near-infrared Diagnostics: Stars Gas and Kinematicsmentioning

confidence: 99%

A Sinfoni View of Galaxy Centers: Morphology and Kinematics of Five Nuclear Star-Formation Rings

Böker

Falcón-Barroso

Schinnerer

et al. 2008

The Astronomical Journal

109

164

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We present near-infrared (H -and K-band) integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. The data, obtained at the Very Large Telescope with the SINFONI spectrograph, are used to construct maps of various emission lines that reveal the individual star forming regions ("hot spots") delineating the rings. We derive the morphological parameters of the rings, and construct velocity fields of the stars and the emission line gas. We propose a qualitative, but robust, diagnostic for relative hot spot ages based on the intensity ratios of the emission lines Brγ , He i, and [Fe ii]. Application of this diagnostic to the data presented here provides tentative support for a scenario in which star formation in the rings is triggered predominantly at two well-defined regions close to, and downstream from, the intersection of dust lanes along the bar with the inner Lindblad resonance.

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“…Amongst the small fraction of the ionizing stars that can be seen in the K-band, the dominant spectral signature is nebular emission in Brγ and in some cases He i, with H 2 usually also seen (Hanson et al 2002). In principal, nebular He i and Brγ emission lines can be used as indirect probes of the ionizing star (Lumsden et al 2001), although mid-IR fine structure lines offer a more sensitive probe, and direct spectroscopic classification is, of course, preferable to both. Near-IR stellar spectroscopy is more straightforward for sources within the same star forming complexes as UCHII regions, albeit away from the strong nebulosity (Bik et al 2005).…”

Section: Near-ir Observation Of Uchii Regionsmentioning

confidence: 99%

Near and mid infrared observations of ultracompact HII regions

Crowther¹

2005

Proc. IAU

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Abstract. This review discusses near-and mid-infrared observations of Ultracompact (UC) HII regions. The importance of ISO mid-IR fine-structure nebular lines is emphasised, since only a small fraction of UCHII regions are observed directly in the near-IR. The reliability of contemporary atmospheric models for such indirect diagnostics is discussed, whilst a revised spectral type-temperature calibration is presented for Galactic O3 to B3 dwarfs. In particular, fine-structure line derived properties of G29.96-0.02 differ from the direct near-IR spectroscopic result and represents a serious discrepancy which needs to be addressed. Mid-IR MSX and Spitzer imaging permits the identification of those UCHII regions for which far-IR IRAS fluxes are reliable, relevant to the single versus cluster nature of individual sources. High spatial resolution imaging with ground-based 8m telescopes allows more direct tests, as recently applied to G70.29+1.60. Finally, recent Spitzer mid-IR observations of Giant HII regions are briefly discussed.

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Infrared helium-hydrogen line ratios as a measure of stellar effective temperature

Cited by 21 publications

References 44 publications

VLT-SINFONI integral field spectroscopy of low-zluminous and ultraluminous infrared galaxies

VLT-SINFONI integral field spectroscopy of low-zluminous and ultraluminous infrared galaxies

A Sinfoni View of Galaxy Centers: Morphology and Kinematics of Five Nuclear Star-Formation Rings

Near and mid infrared observations of ultracompact HII regions

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