The<i>Herschel</i>Exploitation of Local Galaxy Andromeda (HELGA)

Viaene, S.; Fritz, J.; Baes, M.; Bendo, G. J.; Blommaert, J. A. D. L.; Boquien, M.; Boselli, A.; Ciesla, L.; Cortese, Luca; Looze, I. De; Gear, Walter Kieran; Gentile, Gianfranco; Hughes, T. M.; Jarrett, T. H.; Karczewski, O. Ł.; Smith, M.; Spinoglio, L.; Tamm, A.; Tempel, Elmo; Thilker, David A.; Verstappen, J.

doi:10.1051/0004-6361/201423534

Cited by 65 publications

(122 citation statements)

References 106 publications

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“…If the dust-to-gas mass ratio is similar on both sides, according to Viaene et al (2014) we expect a gas mass a factor of 3 larger on this side (see Table 2). Similarly, when one averages the observed column densities of molecular hydrogen Pos.…”

Section: Description Of the Detectionsmentioning

confidence: 91%

“…We extracted different parameters relevant for our study from the work of Viaene et al (2014) and Draine et al (2014). These parameters are summarised in Table 2.…”

Section: Infrared Datamentioning

confidence: 99%

“…They estimate cold dust temperatures, which are similar to those derived from Draine et al (2014), as shown in Table 2. The differences could be accounted for by the different datasets used as well as different modelling, Viaene et al (2014) directly fit the spectral energy distribution, while Draine et al (2014) relies on a physical model. Viaene et al (2014) have also provided a warm dust temperature (labelled "birth cloud" in their paper) larger than in the surrounding regions.…”

Section: Infrared Datamentioning

confidence: 99%

“…The differences could be accounted for by the different datasets used as well as different modelling, Viaene et al (2014) directly fit the spectral energy distribution, while Draine et al (2014) relies on a physical model. Viaene et al (2014) have also provided a warm dust temperature (labelled "birth cloud" in their paper) larger than in the surrounding regions. This suggests that there are substructures linked to recent star formation, corresponding to (weak) star-forming activity (3-15 M /Myr).…”

Section: Infrared Datamentioning

confidence: 99%

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Dense gas tracing the collisional past of Andromeda

Melchior

Combes

2015

A&A

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The central kiloparsec region of the Andromeda galaxy is relatively gas poor, while the interstellar medium appears to be concentrated in a ring-like structure at about 10 kpc radius. The central gas depletion has been attributed to a possible head-on collision 200 Myr ago, supported by the existence of an offset inner ring of warm dust. We present new IRAM 30 m radio telescope observations of the molecular gas in the central region, and the detection of CO and its isotopes 13 CO(2−1) and C 18 O(2−1), together with the dense gas tracers, HCN(1−0) and HCO+(1−0). A systematic study of the observed peak temperatures with non-local thermal equilibrium simulations shows that the detected lines trace dense regions with n H 2 in the range 2.5 × 10 4 −5.6 × 10 5 cm −3 , while the gas is very clumpy with a beam filling factor of 0.5−2 × 10 −2 . This is compatible with the dust mass derived from the far-infrared emission, assuming a dust-to-gas mass ratio of 0.01 with a typical clump size of 2 pc. We also show that the gas is optically thin in all lines except for 12 CO(1-0) and 12 CO(2-1), CO lines are close to their thermal equilibrium condition at 17-20 K, the molecular hydrogen density is larger than critical, and HCN and HCO+ lines have a subthermal excitation temperature of 9 K with a density smaller than critical. The average 12 CO/ 13 CO line ratio is high (∼21), and close to the 12 CO/C 18 O ratio (∼30) that was measured in the north-western region and estimated in the south-east stacking. The fact that the optically thin 13 CO and C 18 O lines have comparable intensities means that the secondary element 13 C is depleted with respect to the primary 12 C, as is expected just after a recent star formation. This suggests that there has been a recent starburst in the central region, supporting the head-on collision scenario.

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Section: Description Of the Detectionsmentioning

confidence: 91%

“…We extracted different parameters relevant for our study from the work of Viaene et al (2014) and Draine et al (2014). These parameters are summarised in Table 2.…”

Section: Infrared Datamentioning

confidence: 99%

Section: Infrared Datamentioning

confidence: 99%

Section: Infrared Datamentioning

confidence: 99%

See 2 more Smart Citations

Dense gas tracing the collisional past of Andromeda

Melchior

Combes

2015

A&A

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“…The study of a single infrared surface brightness ratio has the advantage of being mainly sensitive to dust temperature changes. The exploration of multi-waveband dust spectal energy distribution (SED) fitting techniques, however, benefits from the broader wavelength coverage to study the different heating sources in several infrared wavebands (e.g., Montalto et al 2009;Aniano et al 2012;Dale et al 2012;Mentuch Cooper et al 2012;Smith et al 2012;Ciesla et al 2014;Viaene et al 2014). Panchromatic SED fitting methods are even capable of constraining the absorbed energy from star light and re-emitted photons from dust grains by postulating a dust energy balance (e.g., CIGALE, MAGPHYS and GRASIL among others).…”

Section: Introductionmentioning

confidence: 99%

High-resolution, 3D radiative transfer modeling

Looze

Fritz

Baes

et al. 2014

A&A

114

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Context. Dust reprocesses about half of the stellar radiation in galaxies. The thermal re-emission by dust of absorbed energy is considered to be driven merely by young stars so is often applied to tracing the star formation rate in galaxies. Recent studies have argued that the old stellar population might be responsible for a non-negligible fraction of the radiative dust heating. Aims. In this work, we aim to analyze the contribution of young ( < ∼ 100 Myr) and old (∼10 Gyr) stellar populations to radiative dust heating processes in the nearby grand-design spiral galaxy M 51 using radiative transfer modeling. High-resolution 3D radiative transfer (RT) models are required to describe the complex morphologies of asymmetric spiral arms and clumpy star-forming regions and to model the propagation of light through a dusty medium. Methods. In this paper, we present a new technique developed to model the radiative transfer effects in nearby face-on galaxies. We construct a high-resolution 3D radiative transfer model with the Monte-Carlo code SKIRT to account for the absorption, scattering, and non-local thermal equilibrium (NLTE) emission of dust in M 51. The 3D distribution of stars is derived from the 2D morphology observed in the IRAC 3.6 µm, GALEX FUV, Hα, and MIPS 24 µm wavebands, assuming an exponential vertical distribution with an appropriate scale height. The dust geometry is constrained through the far-ultraviolet (FUV) attenuation, which is derived from the observed total-infrared-to-far-ultraviolet luminosity ratio. The stellar luminosity, star formation rate, and dust mass have been scaled to reproduce the observed stellar spectral energy distribution (SED), FUV attenuation, and infrared SED. Results. The dust emission derived from RT calculations is consistent with far-infrared and submillimeter observations of M 51, implying that the absorbed stellar energy is balanced by the thermal re-emission of dust. The young stars provide 63% of the energy for heating the dust responsible for the total infrared emission (8−1000 µm), while 37% of the dust emission is governed through heating by the evolved stellar population. In individual wavebands, the contribution from young stars to the dust heating dominates at all infrared wavebands but gradually decreases towards longer infrared and submillimeter wavebands for which the old stellar population becomes a non-negligible source of heating. Upon extrapolation of the results for M 51, we present prescriptions for estimating the contribution of young stars to the global dust heating based on a tight correlation between the dust heating fraction and specific star formation rate.

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Planckintermediate results

Ade

Aghanim

Arnaud

et al. 2015

A&A

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The Andromeda galaxy (M 31) is one of a few galaxies that has sufficient angular size on the sky to be resolved by the Planck satellite. Planck has detected M 31 in all of its frequency bands, and has mapped out the dust emission with the High Frequency Instrument, clearly resolving multiple spiral arms and sub-features. We examine the morphology of this long-wavelength dust emission as seen by Planck, including a study of its outermost spiral arms, and investigate the dust heating mechanism across M 31. We find that dust dominating the longer wavelength emission ( > ∼ 0.3 mm) is heated by the diffuse stellar population (as traced by 3.6 µm emission), with the dust dominating the shorter wavelength emission heated by a mix of the old stellar population and star-forming regions (as traced by 24 µm emission). We also fit spectral energy distributions for individual 5 pixels and quantify the dust properties across the galaxy, taking into account these different heating mechanisms, finding that there is a linear decrease in temperature with galactocentric distance for dust heated by the old stellar population, as would be expected, with temperatures ranging from around 22 K in the nucleus to 14 K outside of the 10 kpc ring. Finally, we measure the integrated spectrum of the whole galaxy, which we find to be well-fitted with a global dust temperature of (18.2 ± 1.0) K with a spectral index of 1.62 ± 0.11 (assuming a single modified blackbody), and a significant amount of free-free emission at intermediate frequencies of 20-60 GHz, which corresponds to a star formation rate of around 0.12 M yr −1 . We find a 2.3σ detection of the presence of spinning dust emission, with a 30 GHz amplitude of 0.7 ± 0.3 Jy, which is in line with expectations from our Galaxy.

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TheHerschelExploitation of Local Galaxy Andromeda (HELGA)

Cited by 65 publications

References 106 publications

Dense gas tracing the collisional past of Andromeda

Dense gas tracing the collisional past of Andromeda

High-resolution, 3D radiative transfer modeling

Planckintermediate results

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