Probing changes of dust properties along a chain of solar-type prestellar and protostellar cores in Taurus with NIKA

The characterization of dust properties in the interstellar medium is key for understanding the physics and chemistry of star formation. Mass estimates are crucial to determine gravitational collapse conditions for the birth of new stellar objects in molecular clouds. However, most of these estimates rely on dust models that need further observational constraints to capture the relevant parameter variations depending on the local environment: from clouds to prestellar and protostellar cores. We present results of a new study of dust emissivity changes based on millimeter continuum data obtained with the NIKA camera at the IRAM-30 m telescope. Observing dust emission at 1.15 mm and 2 mm allows us to constrain the dust emissivity index, β, in the Rayleigh-Jeans tail of the dust spectral energy distribution far from its peak emission, where the contribution of other parameters (i.e. dust temperature) is more important. Focusing on the Taurus molecular cloud, one of the most famous low-mass star-forming regions in the Gould Belt, we analyze the emission properties of several distinct objects in the B213 filament. This subparsec-sized region is of particular interest since it is characterized by a collection ofevolutionary stages of early star formation: three prestellar cores, two Class 0/I protostellar cores and one Class II object. We are therefore able to compare dust properties among a sequence of sources that likely derive from the same parent filament. By means of the ratio of the two NIKA channel maps, we show that in the Rayleigh-Jeans approximation, βRJ varies among the objects: it decreases from prestellar cores (βRJ ~ 2) to protostellar cores (βRJ ~ 1) and the Class II object (βRJ ~ 0). For one prestellar and two protostellar cores, we produce a robust study using available Herschel data to constrain the dust temperature of the sources. By using the Abel transform inversion technique we derive accurate radial temperature profiles that allow us to obtain radial β profiles. We find systematic spatial variations of β in the protostellar cores that are not observed in the prestellar core. While in the former case β decreases toward the center (with β varying between 1 and 2), in the latter it remains constant (β = 2.4 ± 0.3). Moreover, the dust emissivity index appears anticorrelated with the dust temperature. We discuss the implication of these results in terms of dust grain evolution between pre- and protostellar cores.

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Dust properties and star formation of approximately a thousand local galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834553 ◽

2019 ◽

Vol 631 ◽

pp. A38 ◽

Cited By ~ 1

Author(s):

S. Lianou ◽

P. Barmby ◽

A. A. Mosenkov ◽

M. Lehnert ◽

O. Karczewski

Keyword(s):

Star Formation ◽

Spectral Energy Distribution ◽

Dust Emission ◽

Distribution Functions ◽

Spectral Energy ◽

Emission Properties ◽

Galaxy Type ◽

Dust Mass ◽

The Galaxy ◽

Stellar Masses

Aims. We derived the dust properties for 753 local galaxies and examine how these relate to some of their physical properties. We present the derived dust emission properties, including model spectral energy distribution (SEDs), star formation rates (SFRs) and stellar masses, as well as their relations. Methods. We modelled the global dust-SEDs for 753 galaxies, treated statistically as an ensemble within a hierarchical Bayesian dust-SED modelling approach, so as to derive their infrared (IR) emission properties. To create the observed dust-SEDs, we used a multi-wavelength set of observations, ranging from near-IR to far-IR-to-submillimeter wavelengths. The model-derived properties are the dust masses (Mdust), the average interstellar radiation field intensities (Uav), the mass fraction of very small dust grains (“QPAH” fraction), as well as their standard deviations. In addition, we used mid-IR observations to derive SFR and stellar masses, quantities independent of the dust-SED modelling. Results. We derive distribution functions of the properties for the galaxy ensemble and as a function of galaxy type. The mean value of Mdust for the early-type galaxies (ETGs) is lower than that for the late-type and irregular galaxies (LTGs and Irs, respectively), despite ETGs and LTGs having stellar masses spanning across the whole range observed. The Uav and “QPAH” fraction show no difference among different galaxy types. When fixing Uav to the Galactic value, the derived “QPAH” fraction varies across the Galactic value (0.071). The specific SFR increases with galaxy type, while this is not the case for the dust-specific SFR (SFR/Mdust), showing an almost constant star formation efficiency per galaxy type. The galaxy sample is characterised by a tight relationship between the dust mass and the stellar mass for the LTGs and Irs, while ETGs scatter around this relation and tend towards smaller dust masses. While the relation indicates that Mdust may fundamentally be linked to M⋆, metallicity and Uav are the second parameter driving the scatter, which we investigate in a forthcoming work. We used the extended Kennicutt–Schmidt (KS) law to estimate the gas mass and the gas-to-dust mass ratio (GDR). The gas mass derived from the extended KS law is on average ∼20% higher than that derived from the KS law, and a large standard deviation indicates the importance of the average star formation present to regulate star formation and gas supply. The average GDR for the LTGs and Irs is 370, and including the ETGs gives an average of 550.

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M 31 circum-nuclear region: A molecular survey with the IRAM interferometer

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834069 ◽

2019 ◽

Vol 625 ◽

pp. A148

Author(s):

Julien Dassa-Terrier ◽

Anne-Laure Melchior ◽

Françoise Combes

Keyword(s):

Star Formation ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Dust Emission ◽

Critical Density ◽

Local Thermal Equilibrium ◽

Spectral Energy ◽

Nuclear Region ◽

Mass Size ◽

Size Relation

We analysed molecular observations performed at IRAM interferometer in CO(1-0) of the circum-nuclear region (within 250 pc) of Andromeda with 2.9″ = 11 pc resolution. We detected 12 molecular clumps in this region, corresponding to a total molecular mass of (8.4 ± 0.4)×104 M⊙. These clumps follow Larson’s mass-size relation, but lie well above the velocity-size relation. We discuss the possibility that these clumps are probably not virialised, but are transient agglomerations of smaller entities that might be virialised. Three of these clumps have been detected in CO(2-1) in a previous work, and we find a temperature line ratio below 0.5 in this work. With a radiative transfer analysis, we show that this gas is in non-local thermal equilibrium with a low excitation temperature (Tex = 5 − 9 K). We find a surface beam filling factor of order 5% and a gas density in the range 60 − 650 cm−3, which is well below the critical density. With a gas-to-stellar mass fraction of 4 × 10−4 and dust-to-gas ratio of 0.01, this quiescent region has exhausted its gas budget. Its spectral energy distribution is compatible with passive templates assembled from elliptical galaxies. While weak dust emission is present in the region, we show that no star formation is present and support the previous results that the dust is heated by the old and intermediate stellar population. We study the possibility that this region lies formally in the low-density part of the Kennicutt-Schmidt law in a regime where the star formation rate estimators are not completely reliable. We confirm the quiescence of the inner part of this galaxy known to lie on the green valley.

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Imaging of 2-mm dust continuum emission towards S106 FIR and its spectral energy distribution

Symposium - International Astronomical Union ◽

10.1017/s0074180900221992 ◽

2002 ◽

Vol 206 ◽

pp. 22-25

Author(s):

Ray S. Furuya ◽

Yoshimi Kitamura ◽

Alwyn Wootten ◽

Mark J. Claussen ◽

Ryohei Kawabe

Keyword(s):

Star Formation ◽

Energy Distribution ◽

Early Phase ◽

Spectral Energy Distribution ◽

Continuum Emission ◽

Spectral Energy ◽

Bolometric Luminosity ◽

The Core ◽

Dust Temperature

The class 0 source S106 FIR is a good candidate to investigate a very early phase of star formation because of the presence of an AU-scale Microjet, discovered by our VLBA H2O maser observations and the absence of an extensive CO outflow. In order to reveal the properties of S106 FIR, we conducted observations of 2-mm continuum emission with the Nobeyama Millmeter Array. We detected a weak compact continuum emission around S106 FIR. We analysed the spectral energy distribution of S106 FIR. It is found that the dust temperature and the β index of the dust opacity range from 31 to 55 K and from 1.4 to 1.6, respectively. Using these results, we computed the mass of the core aound S106 FIR and the bolometric luminosity of 3.1 to 5.8 M⊙ and 230 to 1070 L⊙, respectively.

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Herschel and SCUBA-2 observations of dust emission in a sample of Planck cold clumps

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731921 ◽

2018 ◽

Vol 612 ◽

pp. A71 ◽

Cited By ~ 12

Author(s):

Mika Juvela ◽

Jinhua He ◽

Katherine Pattle ◽

Tie Liu ◽

George Bendo ◽

...

Keyword(s):

Star Formation ◽

Energy Distribution ◽

Emission Spectrum ◽

Spectral Index ◽

Spectral Energy Distribution ◽

Dust Emission ◽

Spectral Energy ◽

Wide Range ◽

Tentative Evidence ◽

Diffuse Clouds

Context. Analysis of all-sky Planck submillimetre observations and the IRAS 100 μm data has led to the detection of a population of Galactic cold clumps. The clumps can be used to study star formation and dust properties in a wide range of Galactic environments. Aims. Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength. Methods. We examined the SEDs at large scales using IRAS, Planck, and Herschel data. At smaller scales, we compared JCMT/SCUBA-2 850 μm maps with Herschel data that were filtered using the SCUBA-2 pipeline. Clumps were extracted using the Fellwalker method, and their spectra were modelled as modified blackbody functions. Results. According to IRAS and Planck data, most fields have dust colour temperatures TC ~ 14–18 K and opacity spectral index values of β = 1.5–1.9. The clumps and cores identified in SCUBA-2 maps have T ~ 13 K and similar β values. There are some indications of the dust emission spectrum becoming flatter at wavelengths longer than 500 μm. In fits involving Planck data, the significance is limited by the uncertainty of the corrections for CO line contamination. The fits to the SPIRE data give a median β value that is slightly above 1.8. In the joint SPIRE and SCUBA-2 850 μm fits, the value decreases to β ~ 1.6. Most of the observed T-β anticorrelation can be explained by noise. Conclusions. The typical submillimetre opacity spectral index β of cold clumps is found to be ~1.7. This is above the values of diffuse clouds, but lower than in some previous studies of dense clumps. There is only tentative evidence of a T-β anticorrelation and β decreasing at millimetre wavelengths.

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The young stellar population of the metal-poor galaxy NGC 6822

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2560 ◽

2019 ◽

Vol 490 (1) ◽

pp. 832-847 ◽

Cited By ~ 1

Author(s):

Olivia C Jones ◽

Michael J Sharp ◽

Megan Reiter ◽

Alec S Hirschauer ◽

M Meixner ◽

...

Keyword(s):

Star Formation ◽

Star Formation Rate ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Initial Mass Function ◽

High Mass ◽

Spectral Energy ◽

Mass Star ◽

Star Formation Regions ◽

Ngc 6822

ABSTRACT We present a comprehensive study of massive young stellar objects (YSOs) in the metal-poor galaxy NGC 6822 using IRAC and MIPS data obtained from the Spitzer Space Telescope. We find over 500 new YSO candidates in seven massive star formation regions; these sources were selected using six colour–magnitude cuts. Via spectral energy distribution fitting to the data with YSO radiative transfer models we refine this list, identifying 105 high-confidence and 88 medium-confidence YSO candidates. For these sources, we constrain their evolutionary state and estimate their physical properties. The majority of our YSO candidates are massive protostars with an accreting envelope in the initial stages of formation. We fit the mass distribution of the Stage I YSOs with a Kroupa initial mass function and determine a global star formation rate of 0.039 $\mathrm{M}_{\odot } \, \mathrm{yr}^{-1}$. This is higher than star formation rate estimates based on integrated UV fluxes. The new YSO candidates are preferentially located in clusters which correspond to seven active high-mass star-formation regions which are strongly correlated with the 8 and 24 μm emission from PAHs and warm dust. This analysis reveals an embedded high-mass star formation region, Spitzer I, which hosts the highest number of massive YSO candidates in NGC 6822. The properties of Spitzer I suggest it is younger and more active than the other prominent H ii and star-formation regions in the galaxy.

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A unique distant submillimeter galaxy with an X-ray-obscured radio-luminous active galactic nucleus

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833434 ◽

2018 ◽

Vol 619 ◽

pp. A76 ◽

Cited By ~ 1

Author(s):

X. W. Shu ◽

Y. Q. Xue ◽

D. Z. Liu ◽

T. Wang ◽

Y. K. Han ◽

...

Keyword(s):

Spectral Analysis ◽

Star Formation ◽

Active Galactic Nucleus ◽

Rest Frame ◽

Spectral Energy Distribution ◽

Dust Emission ◽

Stellar Mass ◽

Spectral Energy ◽

X Ray ◽

Photometric Redshift

Aims. We present a multiwavelength study of an atypical submillimeter galaxy, GH500.30, in the GOODS-North field, with the aim to understand its physical properties of stellar and dust emission, as well as the central active galactic nucleus (AGN) activity. Although it is shown that the source is likely an extremely dusty galaxy at high redshift, its exact position of submillimeter emission is unknown. Methods. We use NOEMA observation at 1.2 mm with subarcsecond resolution to resolve the dust emission, and precisely localize the counterparts at other wavelengths, which allows us to better constrain its stellar and dust spectral energy distribution (SED) as well as redshift. We carry out the new near-infrared (NIR) photometry of GH500.30 observed with HST, and perform panchromatic SED modelling from ultraviolet (UV)/optical to submillimeter. We derive the photometric redshift using both NIR and far-infrared (FIR) SED modeling, and place constraints on the stellar and dust properties such as stellar mass, age, dust attenuation, IR luminosity, and star-formation rate (SFR). The AGN properties are inferred from the X-ray spectral analysis and radio observations, and its contribution to the total IR luminosity is estimated from the broadband SED fittings using MAGPHYS. Results. With the new NOEMA interferometric imaging, we confirm that the source is a unique dusty galaxy. It has no obvious counterpart in the optical and even NIR images observed with HST at λ ≲ 1.4 μm. Photometric-redshift analyses from both stellar and dust SED suggest it to likely be at z ≳ 4, though a lower redshift at z ≳ 3.1 cannot be fully ruled out (at 90% confidence interval). Explaining its unusual optical-to-NIR properties requires an old stellar population (∼0.67 Gyr), coexisting with a very dusty ongoing starburst component. The latter is contributing to the FIR emission, with its rest-frame UV and optical light being largely obscured along our line of sight. If the observed fluxes at the rest-frame optical/NIR wavelengths were mainly contributed by old stars, a total stellar mass of ∼3.5 × 1011 M⊙ would be obtained. An X-ray spectral analysis suggests that this galaxy harbors a heavily obscured AGN with NH = 3.3+2.0−1.7 × 1023 cm−2 and an intrinsic 2–10 keV luminosity of Lx ∼ 2.6 × 1044 erg s−1, which places this object among distant type 2 quasars. The radio emission of the source is extremely bright, which is an order of magnitude higher than the star-formation-powered emission, making it one of the most distant radio-luminous dusty galaxies. Conclusions. The combined characteristics of the galaxy suggest that the source appears to have been caught in a rare but critical transition stage in the evolution of submillimeter galaxies, where we are witnessing the birth of a young AGN and possibly the earliest stage of its jet formation and feedback.

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On the pumping of the CS(v=0) masers in W51 e2e

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3667 ◽

2020 ◽

Author(s):

D J van der Walt ◽

A Ginsburg ◽

C Goddi

Keyword(s):

Spectral Energy Distribution ◽

Dust Emission ◽

High Mass ◽

Rate Equations ◽

Spectral Energy ◽

Mass Star ◽

Model Calculations ◽

Maser Emission ◽

Star Forming ◽

Rotational States

Abstract We present the results of numerically solving the rate equations for the first 31 rotational states of CS in the ground vibrational state to determine the conditions under which the J = 1 − 0, J = 2 − 1 and J = 3 − 2 transitions are inverted to produce maser emission. The essence of our results is that the CS(v=0) masers are collisionally pumped and that, depending on the spectral energy distribution, dust emission can suppress the masers. Apart from the J = 1 − 0 and J = 2 − 1 masers the calculations also show that the J = 3 − 2 transition can be inverted to produce maser emission. It is found that beaming is necessary to explain the observed brightness temperatures of the recently discovered CS masers in W51 e2e. The model calculations suggest that a CS abundance of a few times 10−5 and CS(v=0) column densities of the order 1016 cm−2 are required for these masers. The rarity of the CS masers in high mass star forming regions might be the result of a required high CS abundance as well as due to attenuation of the maser emission inside as well as outside of the hot core.

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High-resolution, 3D radiative transfer modelling

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037476 ◽

2020 ◽

Vol 638 ◽

pp. A150

Author(s):

S. Viaene ◽

A. Nersesian ◽

J. Fritz ◽

S. Verstocken ◽

M. Baes ◽

...

Keyword(s):

Star Formation ◽

Radiative Transfer ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Dust Emission ◽

Realistic Model ◽

Spectral Energy ◽

Nearby Star ◽

Future Evolution ◽

Ngc 1068

The star formation rate and the mass of interstellar medium (ISM) have a high predictive power for the future evolution of a galaxy. Nevertheless, deriving such properties is not straightforward. Dust emission, an important diagnostic of star formation and ISM mass throughout the Universe, can be powered by sources unrelated to ongoing star formation. In the framework of the DustPedia project we set out to disentangle the radiation of the ongoing star formation from that of the older stellar populations. This is done through detailed 3D radiative transfer simulations of face-on spiral galaxies. We take special care in modelling the morphological features present for each source of radiation. In this particular study, we focus on NGC 1068, which in addition contains an active galactic nucleus (AGN). The effect of diffuse dust heating by an AGN (beyond the torus) has so far only been investigated for quasars. This additional dust heating source further contaminates the broadband fluxes that are used by classic galaxy modelling tools to derive physical properties. We aim to fit a realistic model to the observations of NGC 1068 and quantify the contribution of the several dust-heating sources. Our model is able to reproduce the global spectral energy distribution of the galaxy. It matches the resolved optical and infrared images fairly well, but deviates in the UV and the submillimetre (submm). This is partly due to beam smearing effects, but also because the input dust distribution is not sufficiently peaked in the centre. We find that AGN contamination of the broadband fluxes has a strong dependency on wavelength. It peaks in the mid-infrared, drops in the far-infrared, and then rises again at submm wavelengths. We quantify the contribution of the dust-heating sources in each 3D dust cell and find a median value of 83% for the star formation component. The AGN contribution is measurable at the percentage level in the disc, but quickly increases in the inner few hundred parsecs, peaking above 90%. This is the first time the phenomenon of an AGN heating the diffuse dust beyond its torus is quantified in a nearby star-forming galaxy. NGC 1068 only contains a weak AGN, meaning this effect could be stronger in galaxies with a more luminous AGN. This could significantly impact the derived star formation rates and ISM masses for such systems.

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The effects of star formation history in the SFR–M* relation of H ii galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3333 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3240-3253

Author(s):

Amanda R Lopes ◽

Eduardo Telles ◽

Jorge Melnick

Keyword(s):

Star Formation ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Star Formation History ◽

Spectral Energy ◽

Distribution Fitting ◽

Good Tool ◽

Star Forming ◽

Additional Information ◽

Star Formation Histories

ABSTRACT We discuss the implications of assuming different star formation histories (SFH) in the relation between star formation rate (SFR) and mass derived by the spectral energy distribution fitting (SED). Our analysis focuses on a sample of H ii galaxies, dwarf starburst galaxies spectroscopically selected through their strong narrow emission lines in SDSS DR13 at z < 0.4, cross-matched with photometric catalogues from GALEX, SDSS, UKIDSS, and WISE. We modelled and fitted the SEDs with the code CIGALE adopting different descriptions of SFH. By adding information from different independent studies, we find that H ii galaxies are best described by episodic SFHs including an old (10 Gyr), an intermediate age (100−1000 Myr) and a recent population with ages < 10 Myr. H ii galaxies agree with the SFR−M* relation from local star-forming galaxies, and only lie above such relation when the current SFR is adopted as opposed to the average over the entire SFH. The SFR−M* demonstrated not to be a good tool to provide additional information about the SFH of H ii galaxies, as different SFH present a similar behaviour with a spread of <0.1 dex.

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Ammonia observations towards the Aquila Rift cloud complex

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037659 ◽

2020 ◽

Vol 643 ◽

pp. A178

Author(s):

Kadirya Tursun ◽

Jarken Esimbek ◽

Christian Henkel ◽

Xindi Tang ◽

Gang Wu ◽

...

Keyword(s):

Star Formation ◽

Dust Emission ◽

Turbulent Energy ◽

Gravitational Energy ◽

High Mass ◽

Kinetic Temperature ◽

Mass Star ◽

Dense Gas ◽

Star Formation Region ◽

Formation Region

We surveyed the Aquila Rift complex including the Serpens South and W 40 regions in the NH3 (1,1) and (2,2) transitions making use of the Nanshan 26-m telescope. Our observations cover an area of ~ 1.5° × 2.2° (11.4 pc × 16.7 pc). The kinetic temperatures of the dense gas in the Aquila Rift complex obtained from NH3 (2,2)/(1,1) ratios range from 8.9 to 35.0 K with an average of 15.3 ± 6.1 K (errors are standard deviations of the mean). Low gas temperatures are associated with Serpens South ranging from 8.9 to 16.8 K with an average of 12.3 ± 1.7 K, while dense gas in the W 40 region shows higher temperatures ranging from 17.7 to 35.0 K with an average of 25.1 ± 4.9 K. A comparison of kinetic temperatures derived from para-NH3 (2,2)/(1,1) against HiGal dust temperatures indicates that the gas and dust temperatures are in agreement in the low-mass-star formation region of Serpens South. In the high-mass-star formation region W 40, the measured gas kinetic temperatures are higher than those of the dust. The turbulent component of the velocity dispersion of NH3 (1,1) is found to be positively correlated with the gas kinetic temperature, which indicates that the dense gas may be heated by dissipation of turbulent energy. For the fractional total-NH3 (para+ortho) abundance obtained by a comparison with Herschel infrared continuum data representing dust emission, we find values from 0.1 ×10−8 to 2.1 ×10−7 with an average of 6.9 (±4.5) × 10−8. Serpens South also shows a fractional total-NH3 (para+ortho) abundance ranging from 0.2 ×10−8 to 2.1 ×10−7 with an average of 8.6 (±3.8) × 10−8. In W 40, values are lower, between 0.1 and 4.3 ×10−8 with an average of 1.6 (±1.4) × 10−8. Weak velocity gradients demonstrate that the rotational energy is a negligible fraction of the gravitational energy. In W 40, gas and dust temperatures are not strongly dependent on the projected distance to the recently formed massive stars. Overall, the morphology of the mapped region is ring-like, with strong emission at lower and weak emission at higher Galactic longitudes. However, the presence of a physical connection between the two parts remains questionable.

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