Context. Supernovae remnants (SNRs) represent a major source of feedback from stars on the interstellar medium of galaxies. During the latest stage of supernova explosions (which lasts 10–100 kyr), ...shock waves produced by the initial blast modify the chemistry of gas and dust, inject kinetic energy in the surroundings, and may alter star formation characteristics. Simultaneously, γ-ray emission is generated by the interaction between the ambient medium and cosmic rays, in particular those locally accelerated in the early stages of the explosion. Aims. We aim to estimate the total molecular mass, local density, and total column density of H2 and the temperature structure in a shocked clump interacting with the supernova remnant IC443 located in a region where cosmic rays interact with the interstellar medium. Measuring the mass of the dense and neutral component of the medium is a prerequisite to understanding the chemistry, energetics, and GeV to TeV γ-ray emission. Methods. Assuming that the emission of H2 pure rotational lines is produced by a collection of gas layers with variable temperature, we compared Spitzer/IRS emission maps for the ν = 0–0 S(0) to S(7) lines with a thermal admixture model. Our description is based on a power-law distribution of thermalized components with temperatures varying between Tmin = 25 K and Tmax = 1500 K. Results. Our thermal admixture model allows the level populations of H2 to be described by a power-law distribution dN = ΛT−ΓdT, with Γ ~ 2.2−4.7. We measured a total mass MH2 = 220−80+110 M⊙ across the Spitzer/IRS field of observations. Conclusions. Our analysis shows that an estimate of the cold molecular gas temperature is paramount to accurately constraining the H2 mass, although the mass remains affected by significant uncertainties due to the assumptions on the gas temperature distribution.
Abstract
We present a catalog of 315 protostellar outflow candidates detected in SiO
J
= 5 − 4 in the ALMA-IMF Large Program, observed with ∼2000 au spatial resolution, 0.339 km s
−1
velocity ...resolution, and 2–12 mJy beam
−1
(0.18–0.8 K) sensitivity. We find median outflow masses, momenta, and kinetic energies of ∼0.3
M
⊙
, 4
M
⊙
km s
−1
, and 10
45
erg, respectively. Median outflow lifetimes are 6000 yr, yielding median mass, momentum, and energy rates of
M
̇
= 10
−4.4
M
⊙
yr
−1
,
P
̇
= 10
−3.2
M
⊙
km s
−1
yr
−1
, and
E
̇
= 1
L
⊙
. We analyze these outflow properties in the aggregate in each field. We find correlations between field-aggregated SiO outflow properties and total mass in cores (∼3
σ
–5
σ
), and no correlations above 3
σ
with clump mass, clump luminosity, or clump luminosity-to-mass ratio. We perform a linear regression analysis and find that the correlation between field-aggregated outflow mass and total clump mass—which has been previously described in the literature—may actually be mediated by the relationship between outflow mass and total mass in cores. We also find that the most massive SiO outflow in each field is typically responsible for only 15%–30% of the total outflow mass (60% upper limit). Our data agree well with the established mechanical force−bolometric luminosity relationship in the literature, and our data extend this relationship up to
L
≥ 10
6
L
⊙
and
P
̇
≥ 1
M
⊙
km s
−1
yr
−1
. Our lack of correlation with clump
L
/
M
is inconsistent with models of protocluster formation in which all protostars start forming at the same time.
We present a catalog of 315 protostellar outflow candidates detected in SiO J=5-4 in the ALMA-IMF Large Program, observed with ~2000 au spatial resolution, 0.339 km/s velocity resolution, and 2-12 ...mJy/beam (0.18-0.8 K) sensitivity. We find median outflow masses, momenta, and kinetic energies of ~0.3 M\(_{\odot}\), 4 M\(_{\odot}\) km/s, and 10\(^{45}\) erg, respectively. Median outflow lifetimes are 6,000 years, yielding median mass, momentum, and energy rates of \(\dot{M}\) = 10\(^{-4.4}\) M\(_{\odot}\) yr\(^{-1}\), \(\dot{P}\) = 10\(^{-3.2}\) M\(_{\odot}\) km/s yr\(^{-1}\), and \(\dot{E}\) = 1 L\(_{\odot}\). We analyze these outflow properties in the aggregate in each field. We find correlations between field-aggregated SiO outflow properties and total mass in cores (~3\(-\)5\(\sigma\)), and no correlations above 3\(\sigma\) with clump mass, clump luminosity, or clump luminosity-to-mass ratio. We perform a linear regression analysis and find that the correlation between field-aggregated outflow mass and total clump mass - which has been previously described in the literature - may actually be mediated by the relationship between outflow mass and total mass in cores. We also find that the most massive SiO outflow in each field is typically responsible for only 15-30% of the total outflow mass (60% upper limit). Our data agree well with the established mechanical force-bolometric luminosity relationship in the literature, and our data extend this relationship up to L \(\geq\) 10\(^6\) L\(_{\odot}\) and \(\dot{P}\) \(\geq\) 1 M\(_{\odot}\) km/s yr\(^{-1}\). Our lack of correlation with clump L/M is inconsistent with models of protocluster formation in which all protostars start forming at the same time.
Context.
Supernova remnants (SNRs) represent a major feedback source from stars in the interstellar medium of galaxies. During the latest stage of supernova explosions, shock waves produced by the ...initial blast modify the chemistry of gas and dust, inject kinetic energy into the surroundings, and may alter star formation characteristics. Simultaneously,
γ
-ray emission is generated by the interaction between the ambient medium and cosmic rays (CRs), including those accelerated in the early stages of the explosion.
Aims.
We study the stellar and interstellar contents of IC443, an evolved shell-type SNR at a distance of 1.9 kpc with an estimated age of 30 kyr. We aim to measure the mass of the gas and characterize the nature of infrared point sources within the extended G region, which corresponds to the peak of
γ
-ray emission detected by VERITAS and
Fermi
.
Methods.
We performed 10′ × 10′ mapped observations of
12
CO,
13
CO
J
= 1–0,
J
= 2–1, and
J
= 3–2 pure rotational lines, as well as C
18
O
J
= 1–0 and
J
= 2–1 obtained with the IRAM 30 m and APEX telescopes over the extent of the
γ
-ray peak to reveal the molecular structure of the region. We first compared our data with local thermodynamic equilibrium models. We estimated the optical depth of each line from the emission of the isotopologs
13
CO and C
18
O. We used the population diagram and large velocity gradient assumption to measure the column density, mass, and kinetic temperature of the gas using
12
CO and
13
CO lines. We used complementary data (stars, gas, and dust at multiple wavelengths) and infrared point source catalogs to search for protostar candidates.
Results.
Our observations reveal four molecular structures: a shocked molecular clump associated with emission lines extending between −31 and 16 km s
−1
, a quiescent, dark cloudlet associated with a line width of ~2 km s
−1
, a narrow ring-like structure associated with a line width of ~1.5 km s
−1
, and a shocked knot. We measured a total mass of ~230, ~90, ~210, and ~4
M
⊙
, respectively, for the cloudlet, ring-like structure, shocked clump, and shocked knot. We measured a mass of ~1100
M
⊙
throughout the rest of the field of observations where an ambient cloud is detected. We found 144 protostar candidates in the region.
Conclusions.
Our results emphasize how the mass associated with the ring-like structure and the cloudlet cannot be overlooked when quantifying the interaction of CRs with the dense local medium. Additionally, the presence of numerous possible protostars in the region might represent a fresh source of CRs, which must also be taken into account in the interpretation of
γ
-ray observationsin this region.
A crucial aspect in addressing the challenge of measuring the core mass function (CMF), that is pivotal for comprehending the origin of the initial mass function (IMF), lies in constraining the ...temperatures of the cores. We aim to measure the luminosity, mass, column density and dust temperature of star-forming regions imaged by the ALMA-IMF large program. These fields were chosen to encompass early evolutionary stages of massive protoclusters. High angular resolution mapping is required to capture the properties of protostellar and pre-stellar cores within these regions, and to effectively separate them from larger features, such as dusty filaments. We employed the point process mapping (PPMAP) technique, enabling us to perform spectral energy distribution fitting of far-infrared and submillimeter observations across the 15 ALMA-IMF fields, at an unmatched 2.5$^ prime $ angular resolution. By combining the modified blackbody model with near-infrared data, we derived bolometric luminosity maps. We estimated the errors impacting values of each pixel in the temperature, column density, and luminosity maps. Subsequently, we employed the extraction algorithm getsf on the luminosity maps in order to detect luminosity peaks and measure their associated masses. We obtained high-resolution constraints on the luminosity, dust temperature, and mass of protoclusters, that are in agreement with previously reported measurements made at a coarser angular resolution. We find that the luminosity-to-mass ratio correlates with the evolutionary stage of the studied regions, albeit with intra-region variability. We compiled a PPMAP source catalog of 313 luminosity peaks using getsf on the derived bolometric luminosity maps. The PPMAP source catalog provides constraints on the mass and luminosity of protostars and cores, although one source may encompass several objects. Finally, we compare the estimated luminosity-to-mass ratio of PPMAP sources with evolutionary tracks and discuss the limitations imposed by the 2.5$^ prime $ beam.
The star formation process leads to an increased chemical complexity in the interstellar medium. Sites associated with high-mass star and cluster formation exhibit a so-called hot core phase, ...characterized by high temperatures and column densities of complex organic molecules. We aim to systematically search for and identify a sample of hot cores toward the 15 Galactic protoclusters of the ALMA-IMF Large Program and investigate their statistical properties. We built a comprehensive census of hot core candidates toward the ALMA-IMF protoclusters based on the detection of two mf emission lines at 216.1\,GHz. We used the source extraction algorithm GExt2D to identify peaks of methyl formate ( emission, a complex species commonly observed toward sites of star formation. We performed a cross-matching with the catalog of thermal dust continuum sources from the ALMA-IMF 1.3\,mm continuum data to infer their physical properties. We built a catalog of 76 hot core candidates with masses ranging from sim 0.2\,Msun to sim 80\,Msun , of which 56 are new detections. A large majority of these objects, identified from methyl formate emission, are compact and rather circular, with deconvolved full width at half maximum (FWHM) sizes of sim \,2300\,au on average. The central sources of two target fields show more extended, but still rather circular, methyl formate emission with deconvolved FWHM sizes of sim 6700\,au and 13400\,au. About 30<!PCT!> of our sample of methyl formate sources have core masses above 8\,Msun and range in size from sim \,1000\,au to 13400\,au, which is in line with measurements of archetypical hot cores. The origin of the emission toward the lower-mass cores may be explained as a mixture of contributions from shocks or may correspond to objects in a more evolved state (i.e., beyond the hot core stage). We find that the fraction of hot core candidates increases with the core mass, suggesting that the brightest dust cores are all in the hot core phase. Our results suggest that most of these compact methyl formate sources are readily explained by simple symmetric models, while collective effects from radiative heating and shocks from compact protoclusters are needed to explain the observed extended mf emission. The large fraction of hot core candidates toward the most massive cores suggests that they rapidly enter the hot core phase and that feedback effects from the forming protostar(s) impact their environment on short timescales.
Context . Supernovae remnants (SNRs) represent a major source of feedback from stars on the interstellar medium of galaxies. During the latest stage of supernova explosions (which lasts 10–100 kyr), ...shock waves produced by the initial blast modify the chemistry of gas and dust, inject kinetic energy in the surroundings, and may alter star formation characteristics. Simultaneously, γ -ray emission is generated by the interaction between the ambient medium and cosmic rays, in particular those locally accelerated in the early stages of the explosion. Aims . We aim to estimate the total molecular mass, local density, and total column density of H 2 and the temperature structure in a shocked clump interacting with the supernova remnant IC443 located in a region where cosmic rays interact with the interstellar medium. Measuring the mass of the dense and neutral component of the medium is a prerequisite to understanding the chemistry, energetics, and GeV to TeV γ -ray emission. Methods . Assuming that the emission of H 2 pure rotational lines is produced by a collection of gas layers with variable temperature, we compared Spitzer/IRS emission maps for the ν = 0–0 S(0) to S(7) lines with a thermal admixture model. Our description is based on a power-law distribution of thermalized components with temperatures varying between T min = 25 K and T max = 1500 K. Results . Our thermal admixture model allows the level populations of H 2 to be described by a power-law distribution dN = Λ T −Γ d T , with Γ ~ 2.2−4.7. We measured a total mass M H 2 = 220 −80 +110 M ⊙ across the Spitzer/IRS field of observations. Conclusions . Our analysis shows that an estimate of the cold molecular gas temperature is paramount to accurately constraining the H 2 mass, although the mass remains affected by significant uncertainties due to the assumptions on the gas temperature distribution.
ALMA-IMF Armante, M; Gusdorf, A; Louvet, F ...
Astronomy and astrophysics (Berlin),
06/2024, Letnik:
686
Journal Article
Recenzirano
Context. One of the central questions in astrophysics is the origin of the initial mass function (IMF). It is intrinsically linked to the processes from which it originates, and hence its connection ...with the core mass function (CMF) must be elucidated. Aims. We aim to measure the CMF in the evolved W33-Main star-forming protocluster to compare it with CMF recently obtained in other Galactic star-forming regions, including the ones that are part of the ALMA-IMF program. Methods. We used observations from the ALMA-IMF large programme: ~2′ × 2′ maps of emission from the continuum and selected lines at 1.3 mm and 3 mm observed by the ALMA 12m only antennas. Our angular resolution was typically 1″, that is, ~2400 au at a distance of 2.4 kpc. The lines we analysed are CO (2–1), SiO (5–4), N2H+ (1–0), H41α as well as He41α blended with C41α. We built a census of dense cores in the region, and we measured the associated CMF based on a core-dependent temperature value. Results. We confirmed the ‘evolved’ status of W33-Main by identifiying three H II regions within the field, and to a lesser extent based on the number and extension of N2H+ filaments. We produced a filtered core catalogue of 94 candidates that we refined to take into account the contamination of the continuum by free-free and line emission, obtaining 80 cores with masses that range from 0.03 to 13.2 M⊙. We fitted the resulting high-mass end of the CMF with a single power law of the form N(log(M)) ∝ Mα, obtaining α = −1.44−0.22+0.16, which is slightly steeper but consistent with the Salpeter index. We categorised our cores as prestellar and protostellar, mostly based on outflow activity and hot core nature. We found the prestellar CMF to be steeper than a Salpeter-like distribution, and the protostellar CMF to be slightly top heavy. We found a higher proportion of cores within the H II regions and their surroundings than in the rest of the field. We also found that the cores’ masses were rather low (maximum mass of ~13 M⊙). Conclusions. We find that star formation in W33-Main could be compatible with a ‘clump-fed’ scenario of star formation in an evolved cloud characterised by stellar feedback in the form of H II regions, and under the influence of massive stars outside the field. Our results differ from those found in less evolved young star-forming regions in the ALMA-IMF program. Further investigations are needed to elucidate the evolution of late CMFs towards the IMF over statistically significant samples.
ALMA-IMF Armante, M.; Gusdorf, A.; Louvet, F. ...
Astronomy and astrophysics (Berlin),
6/2024, Letnik:
686
Journal Article
Recenzirano
Odprti dostop
Context. One of the central questions in astrophysics is the origin of the initial mass function (IMF). It is intrinsically linked to the processes from which it originates, and hence its connection ...with the core mass function (CMF) must be elucidated. Aims. We aim to measure the CMF in the evolved W33-Main star-forming protocluster to compare it with CMF recently obtained in other Galactic star-forming regions, including the ones that are part of the ALMA-IMF program. Methods. We used observations from the ALMA-IMF large programme: ~2′ × 2′ maps of emission from the continuum and selected lines at 1.3 mm and 3 mm observed by the ALMA 12m only antennas. Our angular resolution was typically 1″, that is, ~2400 au at a distance of 2.4 kpc. The lines we analysed are CO (2–1), SiO (5–4), N 2 H+ (1–0), H41α as well as He41α blended with C41α. We built a census of dense cores in the region, and we measured the associated CMF based on a core-dependent temperature value. Results. We confirmed the ‘evolved’ status of W33-Main by identifiying three H II regions within the field, and to a lesser extent based on the number and extension of N 2 H + filaments. We produced a filtered core catalogue of 94 candidates that we refined to take into account the contamination of the continuum by free-free and line emission, obtaining 80 cores with masses that range from 0.03 to 13.2 M ⊙ . We fitted the resulting high-mass end of the CMF with a single power law of the form N(log(M)) ∝ M α , obtaining α = −1.44 −0.22 +0.16 , which is slightly steeper but consistent with the Salpeter index. We categorised our cores as prestellar and protostellar, mostly based on outflow activity and hot core nature. We found the prestellar CMF to be steeper than a Salpeter-like distribution, and the protostellar CMF to be slightly top heavy. We found a higher proportion of cores within the H II regions and their surroundings than in the rest of the field. We also found that the cores’ masses were rather low (maximum mass of ~13 M ⊙ ). Conclusions. We find that star formation in W33-Main could be compatible with a ‘clump-fed’ scenario of star formation in an evolved cloud characterised by stellar feedback in the form of H II regions, and under the influence of massive stars outside the field. Our results differ from those found in less evolved young star-forming regions in the ALMA-IMF program. Further investigations are needed to elucidate the evolution of late CMFs towards the IMF over statistically significant samples.
ALMA-IMF Pouteau, Y.; Motte, F.; Nony, T. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
Recenzirano
Odprti dostop
Context.
Among the most central open questions regarding the initial mass function (IMF) of stars is the impact of environment on the shape of the core mass function (CMF) and thus potentially on the ...IMF.
Aims.
The ALMA-IMF Large Program aims to investigate the variations in the core distributions (CMF and mass segregation) with cloud characteristics, such as the density and kinematic of the gas, as diagnostic observables of the formation process and evolution of clouds. The present study focuses on the W43-MM2&MM3 mini-starburst, whose CMF has recently been found to be top-heavy with respect to the Salpeter slope of the canonical IMF.
Methods.
W43-MM2&MM3 is a useful test case for environmental studies because it harbors a rich cluster that contains a statistically significant number of cores (specifically, 205 cores), which was previously characterized in Paper III. We applied a multi-scale decomposition technique to the ALMA 1.3 mm and 3 mm continuum images of W43-MM2&MM3 to define six subregions, each 0.5–1 pc in size. For each subregion we characterized the probability distribution function of the high column density gas,
η
-PDF, using the 1.3 mm images. Using the core catalog, we investigate correlations between the CMF and cloud and core properties, such as the
η
-PDF and the core mass segregation.
Results.
We classify the W43-MM2&MM3 subregions into different stages of evolution, from quiescent to burst to post-burst, based on the surface number density of cores, number of outflows, and ultra-compact HII presence. The high-mass end (>1
M
⊙
) of the subregion CMFs varies from close to the Salpeter slope (quiescent) to top-heavy (burst and post-burst). Moreover, the second tail of the
η
-PDF varies from steep (quiescent) to flat (burst and post-burst), as observed for high-mass star-forming clouds. We find that subregions with flat second
η
-PDF tails display top-heavy CMFs.
Conclusions.
In dynamical environments such as W43-MM2&MM3, the high-mass end of the CMF appears to be rooted in the cloud structure, which is at high column density and surrounds cores. This connection stems from the fact that cores and their immediate surroundings are both determined and shaped by the cloud formation process, the current evolutionary state of the cloud, and, more broadly, the star formation history. The CMF may evolve from Salpeter to top-heavy throughout the star formation process from the quiescent to the burst phase. This scenario raises the question of if the CMF might revert again to Salpeter as the cloud approaches the end of its star formation stage, a hypothesis that remains to be tested.
PDF