The High-mass Protostellar Population of a Massive Infrared Dark Cloud

Moser, Emily; Liu, Mengyao; Tan, Jonathan C.; Lim, Wanggi; Zhang, Yichen; Farias, J. P.

doi:10.3847/1538-4357/ab96c1

Cited by 15 publications

(23 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The slope is flatter than the α = −1.35 for the canonical IMF, in line with the recent estimates for high-mass star-forming regions, that give flatter slopes than those for the low-mass star-forming regions (see, e.g. Motte et al 2018;Liu et al 2018;Cheng et al 2018;Sanhueza et al 2019;Massi et al 2019;Kong 2019;Servajean et al 2019;Moser et al 2020). The fits to the cumulative CMFs for Aquila are also almost invariant with respect to the angular resolution, with an index α −1.32 ± 0.07 indistinguishable from the slope of the canonical IMF, as previously reported by Könyves et al (2015).…”

Section: Angular Resolution Effects In Observationssupporting

confidence: 89%

Strong dependence of the physical properties of cores on spatial resolution in observations and simulations

Louvet

Hennebelle

Didelon

et al. 2021

A&A

View full text Add to dashboard Cite

The angular resolution of a telescope is the primary observational parameter, along with the detector sensitivity in defining the quality of the observed images and of the subsequent scientific exploitation of the data. During the last decade in star formation research, many studies have targeted low- and high-mass star formation regions located at different distances, with different telescopes having specific angular resolution capabilities. However, no dedicated studies of the spatial resolution effects on the derived sizes and masses of the sources extracted from the observed images have been published. We present a systematic investigation of the angular resolution effects, with special attention being paid to the derived masses of sources as well as the shape of the resulting source mass functions (SMFs) and to their comparison with the initial stellar mass function. For our study, we chose two star-forming regions observed with Herschel, NGC 6334 and Aquila distant of 1750 and 460 pc respectively, and three (magneto)-hydrodynamical simulations, virtually positioned at the same distances as the observed regions. We built surface density maps with different angular resolutions by convolving the surface density images of the five regions to a set of four resolutions differing by a factor of two (9, 18, 36, and 72′′), which allowed us to cover spatial resolutions from 0.6 down to 0.02 pc. Then we detected and measured sources in each of the images at each resolution using getsf and we analysed the derived masses and sizes of the extracted sources. We find that the number of sources does not converge from 0.6 to ≳0.05 pc. It increases by about two when the angular resolution increases with a similar factor, which confirms that these large sources are cluster-forming clumps. Below 0.05 pc, the number of source still increases by about 1.3 when the angular resolution increases by two, suggesting that we are close to, but not yet at, convergence. In this regime of physical scales, we find that the measured sizes and masses of sources linearly depend on the angular resolution with no sign of convergence to a resolution-independent value, implying that these sources cannot be assimilated to isolated prestellar cores. The corresponding SMF peak also shifts with angular resolution, while the slope of the high-mass tail of the SMFs remains almost invariant. We propose that these angular resolution effects could be caused by the underestimated background of the unresolved sources observed against the sloping, hill-like backgrounds of the molecular clouds. If prestellar cores physically distinct from their background exist in cluster-forming molecular clouds, we conclude that their mass must be lower than reported so far in the literature. We discuss various implications for the studies of star formation: the problem of determining the mass reservoirs involved in the star-formation process; the inapplicability of the Gaussian beam deconvolution to infer source sizes; and the impossibility to determine the efficiency of the mass conversion from the cores to the stars. Our approach constitutes a simple convergence test to determine whether an observation is affected by angular resolution.

show abstract

Section: Angular Resolution Effects In Observationssupporting

confidence: 89%

Strong dependence of the physical properties of cores on spatial resolution in observations and simulations

Louvet

Hennebelle

Didelon

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…The locations of the ten positions were selected for having relatively high values of Σ and for having a range of star formation activities. In particular, positions P1 to P6 (shown with red circles in Figure 4) are known to be sites of active star formation based on the presence of CO outflows (Kong et al 2019) and containing Herschel-Hi-GAL 70 µm point sources (Moser et al 2020). However, these positions are still dark structures at 8 µm: indeed the P1 to P6 positions correspond approximately to the MIREX Σ peaks of C1, C2, C4, C5, C6 and C8, respectively, identified and characterised by Butler & Tan (2012).…”

Section: Ten Selected Irdc Regionsmentioning

confidence: 99%

“…The positions from P7 to P10 (shown with black circles in Figures 4 and 5) are not directly associated with massive condensations previously identified within the cloud (Rathborne et al 2006;Butler & Tan 2009, 2012 and have been selected for being relatively quiescent in terms of their star formation activity (Kong et al 2019;Moser et al 2020).…”

Section: Ten Selected Irdc Regionsmentioning

confidence: 99%

“…IRDCs are expected to be at a relatively early evolutionary stage, which should simplify their modeling, especially with respect to hot cores (e.g., van der Tak & van Dishoeck 2000;Gieser et al 2019). However, studies with ALMA and Herschel do indicate that active star formation can be proceeding even in MIR-dark regions of the clouds (e.g., Tan et al 2016;Kong et al 2019;Moser et al 2020).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Astrochemical modelling of infrared dark clouds

Entekhabi,

Tan,

Cosentino

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Context. Infrared Dark Clouds (IRDCs) are cold, dense regions of the interstellar medium (ISM) that are likely to represent the initial conditions for massive star and star cluster formation. It is thus important to study the physical and chemical conditions of IRDCs to provide constraints and inputs for theoretical models of these processes. Aims. We aim to determine the astrochemical conditions, especially cosmic ray ionization rate (CRIR) and chemical age, in different regions of the massive IRDC G28.37+00.07 by comparing observed abundances of multiple molecules and molecular ions with the predictions of astrochemical models. Methods. We have computed a series of single-zone, time-dependent, astrochemical models with a gas-grain network that systematically explores the parameter space of density, temperature, CRIR, and visual extinction. We have also investigated the effects of choices of CO ice binding energy and temperatures achieved in transient heating of grains when struck by cosmic rays. We selected 10 positions across the IRDC that are known to have a variety of star formation activity. We utilised mid-infrared (MIR) extinction maps and sub-mm emission maps to measure the mass surface densities of these regions, needed for abundance and volume density estimates. The sub-mm emission maps were also used to measure temperatures. We then used IRAM-30m observations of various tracers, especially C 18 O(1-0), H 13 CO + (1-0), HC 18 O + (1-0), and N 2 H + (1-0), to estimate column densities and thus abundances. Finally, we investigated the range of astrochemical conditions that are consistent with the observed abundances.Results. The typical physical conditions of the IRDC regions are n H ∼ 3 × 10 4 to 10 5 cm −3 and T 10 to 15 K. Strong emission of H 13 CO + (1-0) and N 2 H + (1-0) is detected towards all the positions and these species are used to define relatively narrow velocity ranges of the IRDC regions, which are used for estimates of CO abundances, via C 18 O(1-0). CO depletion factors are estimated to be in the range f D ∼ 3 to 10. Using estimates of the abundances of CO, HCO + and N 2 H + we find consistency with astrochemical models that have relatively low CRIRs of ζ ∼ 10 −18 to ∼ 10 −17 s −1 , with no evidence for systematic variation with the level of star formation activity. Astrochemical ages, defined with reference to an initial condition of all H in H 2 , all C in CO, and all other species in atomic form, are found to be < 1 Myr. We also explore the effects of using other detected species, i.e., HCN, HNC, HNCO, CH 3 OH, and H 2 CO, to constrain the models. These generally lead to implied conditions with higher levels of CRIRs and older chemical ages. Considering the observed f D versus n H relation of the 10 positions, which we find to have relatively little scatter, we discuss potential ways in which the astrochemical models can match such a relation as a quasi-equilibrium limit valid at ages of at least a few free-fall times, i.e., 0.3 Myr, including the effect of CO envelope contamination...

show abstract

“…Of the interstellar molecular clouds that have proved to be fruitful targets for the studies of Galactic star formation, the so-called infrared dark clouds (IRDCs; Pérault et al 1996;Egan et al 1998;Simon et al 2006;Peretto & Fuller 2009) have attracted a lot of interest in recent years (e.g. Tang et al 2019;Soam et al 2019;Peretto et al 2020;Miettinen 2020;Retes-Romero et al 2020;Moser et al 2020 to name a few recent studies). Some of the IRDCs studied so far are found to be associated with early stages of high-mass star formation (e.g.…”

Section: Introductionmentioning

confidence: 99%

Dense cores in the Seahorse infrared dark cloud: physical properties from modified blackbody fits to the far-infrared–submillimetre spectral energy distributions

Miettinen

2020

A&A

View full text Add to dashboard Cite

Context. Infrared dark clouds (IRDCs) can be the birth sites of high-mass stars, and hence determining the physical properties of dense cores in IRDCs is useful to constrain the initial conditions and theoretical models of high-mass star formation. Aims. We aim to determine the physical properties of dense cores in the filamentary Seahorse IRDC G304.74+01.32. Methods. We used data from the Wide-field Infrared Survey Explorer (WISE), Infrared Astronomical Satellite (IRAS), and Herschel in conjuction with our previous 350 and 870 μm observations with the Submillimetre APEX Bolometer Camera (SABOCA) and Large APEX BOlometer CAmera, and constructed the far-IR to submillimetre spectral energy distributions (SEDs) of the cores. The SEDs were fitted using single or two-temperature modified blackbody emission curves to derive the dust temperatures, masses, and luminosities of the cores. Results. For the 12 analysed cores, which include two IR dark cores (no WISE counterpart), nine IR bright cores, and one H II region, the mean dust temperature of the cold (warm) component, the mass, luminosity, H2 number density, and surface density were derived to be 13.3 ± 1.4 K (47.0 ± 5.0 K), 113 ± 29 M⊙, 192 ± 94 L⊙, (4.3 ± 1.2) × 105 cm−3, and 0.77 ± 0.19 g cm−3, respectively. The H II region IRAS 13039-6108a was found to be the most luminous source in our sample ((1.1 ± 0.4) × 103 L⊙). All the cores were found to be gravitationally bound (i.e. the virial parameter αvir < 2). Two out of the nine analysed IR bright cores (22%) were found to follow an accretion luminosity track under the assumptions that the mass accretion rate is 10−5 M⊙ yr−1, the stellar mass is 10% of the parent core mass, and the radius of the central star is 5 R⊙. Most of the remaing ten cores were found to lie within 1 dex below this accretion luminosity track. Seven out of 12 of the analysed cores (58%) were found to lie above the mass-radius thresholds of high-mass star formation proposed in the literature. The surface densities of Σ > 0.4 g cm−3 derived for these seven cores also exceed the corresponding threshold for high-mass star formation. Five of the analysed cores (42%) show evidence of fragmentation into two components in the SABOCA 350 μm image. Conclusions. In addition to the H II region source IRAS 13039-6108a, some of the other cores in Seahorse also appear to be capable of giving birth to high-mass stars. The 22 μm dark core SMM 9 is likely to be the youngest source in our sample that has the potential to form a high-mass star (96 ± 23 M⊙ within a radius of ~0.1 pc). The dense core population in the Seahorse IRDC has comparable average properties to the cores in the well-studied Snake IRDC G11.11-0.12 (e.g. Tdust and L agree within a factor of ~1.8); furthermore, the Seahorse, which lies ~60 pc above the Galactic plane, appears to be a smaller (e.g. three times shorter in projection, ~100 times less massive) version of the Snake. The Seahorse core fragmentation mechanisms appear to be heterogenous, including cases of both thermal and non-thermal Jeans instability. High-resolution follow-up studies are required to address the fragmented cores’ genuine potential of forming high-mass stars.

show abstract

The High-mass Protostellar Population of a Massive Infrared Dark Cloud

Cited by 15 publications

References 40 publications

Strong dependence of the physical properties of cores on spatial resolution in observations and simulations

Strong dependence of the physical properties of cores on spatial resolution in observations and simulations

Astrochemical modelling of infrared dark clouds

Dense cores in the Seahorse infrared dark cloud: physical properties from modified blackbody fits to the far-infrared–submillimetre spectral energy distributions

Contact Info

Product

Resources

About