ABSTRACT In order to investigate star-formation (SF) processes in extreme environments, we have carried out a multi-wavelength analysis of the mid-infrared bubble N46, which hosts a WN7 Wolf-Rayet ...(W-R) star. We have used 13CO line data to trace an expanding shell surrounding the W-R star containing about five condensations within the molecular cloud associated with the bubble. The W-R star is associated with a powerful stellar wind having a mechanical luminosity of ∼4 × 1037 erg s−1. A deviation of the H-band starlight mean polarization angles around the bubble has also been traced, indicating the impact of stellar wind on the surroundings. The Herschel temperature map shows a temperature range of ∼18-24 K toward the five molecular condensations. The photometric analysis reveals that these condensations are associated with the identified clusters of young stellar objects, revealing ongoing SF process. The densest among these five condensations (peak N(H2) ∼9.2 × 1022 cm−2 and AV ∼ 98 mag) is associated with a 6.7 GHz methanol maser, an infrared dark cloud, and the CO outflow, tracing active massive SF within it. At least five compact radio sources (CRSs) are physically linked with the edges of the bubble, and each of them is consistent with the radio spectral class of a B0V-B0.5V-type star. The ages of the individual infrared counterparts of three CRSs (∼1-2 Myr) and a typical age of WN7 W-R star (∼4 Myr) indicate that the SF activities around the bubble are influenced by the feedback of the W-R star.
ABSTRACT We present a detailed study of V899 Mon (a new member in the FUors/EXors family of young low-mass stars undergoing outburst), based on our long-term monitoring of the source starting from ...2009 November to 2015 April. Our optical and near-infrared photometric and spectroscopic monitoring recorded the source transitioning from its first outburst to a short-duration quiescence phase (<1 yr), and then returning to a second outburst. We report here the evolution of the outflows from the inner region of the disk as the accretion rate evolved in various epochs. Our high-resolution (R ∼ 37,000) optical spectrum could resolve interesting clumpy structures in the outflow traced by various lines. Change in far-infrared flux was also detected between two outburst epochs. Based on our observations, we constrained various stellar and envelope parameters of V899 Mon, as well as the kinematics of its accretion and outflow. The photometric and spectroscopic properties of this source fall between classical FUors and EXors. Our investigation of V899 Mon hints at instability associated with magnetospheric accretion being the physical cause of the sudden short-duration pause of the outburst in 2011. It is also a good candidate to explain similar short-duration pauses in outbursts of some other FUors/EXors sources.
We present a multiwavelength study of the Sh2-138, a Galactic compact H ii region. The data comprise of optical and near-infrared (NIR) photometric and spectroscopic observations from the 2-m ...Himalayan Chandra Telescope, radio observations from the Giant Metrewave Radio Telescope (GMRT), and archival data covering radio through NIR wavelengths. A total of 10 Class I and 54 Class II young stellar objects (YSOs) are identified in a 4.6 arcmin×4.6 arcmin area of the Sh2-138 region. Five compact ionized clumps, with four lacking of any optical or NIR counterparts, are identified using the 1280 MHz radio map, and correspond to sources with spectral type earlier than B0.5. Free–free emission spectral energy distribution fitting of the central compact H ii region yields an electron density of ∼2250 ± 400 cm−3. With the aid of a wide range of spectra, from 0.5–15 μm, the central brightest source – previously hypothesized to be the main ionizing source – is characterized as a Herbig Be type star. At large scale (15 arcmin ×15 arcmin), the Herschel images (70–500 μm) and the nearest neighbour analysis of YSOs suggest the formation of an isolated cluster at the junction of filaments. Furthermore, using a greybody fit to the dust spectrum, the cluster is found to be associated with the highest column density (∼3 × 1022 cm−2) and high temperature (∼35 K) regime, as well as with the radio continuum emission. The mass of the central clump seen in the column density map is estimated to be ∼3770 M⊙.
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.
Lean manufacturing applies systematic strategies and tools to eliminate wastes and non-value-added activities in all the functions during manufacturing practice. Similarly, minimizing the consumption ...of material, energy and other natural resources while preserving the environment are the primary focus of sustainable philosophy. The synergy of these two strategies is the need of the hour in order to survive as a manufacturer as well as to achieve sustainability for the industry. The objective of this paper is to present a method of assessment and prioritization of conjoint tools to effectively implement lean and sustainable manufacturing simultaneously using a hybrid of two decision making tools. A multi-criteria decision making tool based on outranking approach, ELECTRE-II (ELimination and Choice Expressing/Translating REality) is implemented for the selection of lean tools in the order of their rankings for achieving sustainability in manufacturing. A case study of a manufacturing industry is presented to illustrate the approach.
Tata Institute of Fundamental Research (TIFR) Near Infrared Imaging Camera-II (TIRCAM2) is a closed-cycle Helium cryo-cooled imaging camera equipped with a Raytheon 512
×
512 pixels InSb Aladdin III ...Quadrant focal plane array (FPA) having sensitivity to photons in the 1–5
μ
m
wavelength band. In this paper, we present the performance of the camera on the newly installed 3.6
m Devasthal Optical Telescope (DOT) based on the calibration observations carried out during 2017 May 11–14 and 2017 October 7–31. After the preliminary characterization, the camera has been released to the Indian and Belgian astronomical community for science observations since 2017 May. The camera offers a field-of-view (FoV) of
∼
8
6
.
5
′
′
×
8
6
.
5
′
′
on the DOT with a pixel scale of 0.169
′
′
. The seeing at the telescope site in the near-infrared (NIR) bands is typically sub-arcsecond with the best seeing of
∼
0
.
4
5
′
′
realized in the NIR
K
-band on 2017 October 16. The camera is found to be capable of deep observations in the
J
,
H
and
K
bands comparable to other 4
m class telescopes available world-wide. Another highlight of this camera is the observational capability for sources up to Wide-field Infrared Survey Explorer (WISE) W1-band (3.4
μ
m) magnitudes of 9.2 in the narrow
L
-band (
n
b
L
;
λ
cen
∼
3.59
μ
m). Hence, the camera could be a good complementary instrument to observe the bright
n
b
L
-band sources that are saturated in the Spitzer-Infrared Array Camera (IRAC) (3.6
≲
7.92 mag) and the WISE W1-band (3.4
≲
8.1 mag). Sources with strong polycyclic aromatic hydrocarbon (PAH) emission at 3.3
μ
m are also detected. Details of the observations and estimated parameters are presented in this paper.
ALMA-IMF Pouteau, Y.; Motte, F.; Nony, T. ...
Astronomy and astrophysics (Berlin),
08/2022, Letnik:
664
Journal Article
Recenzirano
Odprti dostop
Aims.
The processes that determine the stellar initial mass function (IMF) and its origin are critical unsolved problems, with profound implications for many areas of astrophysics. The W43-MM2&MM3 ...mini-starburst ridge hosts a rich young protocluster, from which it is possible to test the current paradigm on the IMF origin.
Methods.
The ALMA-IMF Large Program observed the W43-MM2&MM3 ridge, whose 1.3 mm and 3 mm ALMA 12 m array continuum images reach a ~2500 au spatial resolution. We used both the best-sensitivity and the line-free ALMA-IMF images, reduced the noise with the multi-resolution segmentation technique
MnGSeg
, and derived the most complete and most robust core catalog possible. Using two different extraction software packages,
getsf
and
GExt2D
, we identified ~200 compact sources, whose ~100 common sources have, on average, fluxes consistent to within 30%. We filtered sources with non-negligible free-free contamination and corrected fluxes from line contamination, resulting in a W43-MM2&MM3 catalog of 205
getsf
cores. With a median deconvolved FWHM size of 3400 au, core masses range from ~0.1
M
⊙
to ~70
M
⊙
and the
getsf
catalog is 90% complete down to 0.8
M
⊙
.
Results.
The high-mass end of the core mass function (CMF) of W43-MM2&MM3 is top-heavy compared to the canonical IMF. Fitting the cumulative CMF with a single power-law of the form
N
(> log
M
) ∝
M
α
, we measured
α
= −0.95 ± 0.04, compared to the canonical
α
= −1.35 Salpeter IMF slope. The slope of the CMF is robust with respect to map processing, extraction software packages, and reasonable variations in the assumptions taken to estimate core masses. We explore several assumptions on how cores transfer their mass to stars (assuming a mass conversion efficiency) and subfragment (defining a core fragment mass function) to predict the IMF resulting from the W43-MM2&MM3 CMF. While core mass growth should flatten the high-mass end of the resulting IMF, core fragmentation could steepen it.
Conclusions.
In stark contrast to the commonly accepted paradigm, our result argues against the universality of the CMF shape. More robust functions of the star formation efficiency and core subfragmentation are required to better predict the resulting IMF, here suggested to remain top-heavy at the end of the star formation phase. If confirmed, the IMFs emerging from starburst events could inherit their top-heavy shape from their parental CMFs, challenging the IMF universality.
A total of 64 ATOMS sources at different evolutionary stages were selected to investigate the kinematics and dynamics of gas structures under feedback. We identified dense gas structures based on the ...integrated intensity map of H 13 CO + J = 1−0 emission, and then extracted the average spectra of all the structures to investigate their velocity components and gas kinematics. For the scaling relations between the velocity dispersion, σ , the effective radius, R , and the column density, N , of all the structures, σ − N * R always has a stronger correlation compared to σ − N and σ − R . There are significant correlations between velocity dispersion and column density, which may imply that the velocity dispersion originates in gravitational collapse, also revealed by the velocity gradients. The measured velocity gradients for dense gas structures in early-stage sources and late-stage sources are comparable, indicating gravitational collapse through all evolutionary stages. Late-stage sources do not have large-scale hub-filament structures, but the embedded dense gas structures in late-stage sources show similar kinematic modes to those in early- and middle-stage sources. These results may be explained by the multi-scale hub-filament structures in the clouds. We quantitatively estimated the velocity dispersion generated by the outflows, inflows, ionized gas pressure, and radiation pressure, and found that the ionized gas feedback is stronger than other feedback mechanisms. However, although feedback from HII regions is the strongest, it does not significantly affect the physical properties of the embedded dense gas structures. Combined with the conclusions in our previous work on cloud-clump scales, we suggest that although feedback from cloud to core scales will break up the original cloud complex, the substructures of the original complex can be reorganized into new gravitationally governed configurations around new gravitational centers. This process is accompanied by structural destruction and generation, and changes in gravitational centers, but gravitational collapse is always ongoing.
We present a statistical study of the orientation of outflows with respect to large-scale filaments and magnetic fields. Although filaments are widely observed toward Galactic star-forming regions, ...the exact role of filaments in star formation is unclear. Studies toward low-mass star-forming regions revealed both preferred and random orientations of outflows with respect to the filament long axes, while outflows in massive star-forming regions are mostly oriented perpendicular to the host filaments and parallel to the magnetic fields at similar physical scales. Here, we explore outflows in a sample of 11 protoclusters in H ii regions, a more evolved stage compared to infared dark clouds, using Atacama Large Millimeter/submillimeter Array CO (3-2) line observations. We identify a total of 105 outflow lobes in these protoclusters. Among the 11 targets, 7 are embedded within parsec-scale filamentary structures detected in 13CO line and 870 m continuum emissions. The angles between outflow axes and corresponding filaments (γFil) do not show any hint of preferred orientations (i.e., orthogonal or parallel as inferred in numerical models) with respect to the position angle of the filaments. Identified outflow lobes are also not correlated with the magnetic fields and Galactic plane position angles. Outflows associated with filaments aligned along the large-scale magnetic fields are also randomly oriented. Our study presents the first statistical results of outflow orientation with respect to large-scale filaments and magnetic fields in evolved massive star-forming regions. The random distribution suggests a lack of alignment of outflows with filaments, which may be a result of the evolutionary stage of the clusters.
ALMA–IMF Nony, T.; Galván-Madrid, R.; Motte, F. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
Recenzirano
Odprti dostop
Context.
The origin of the stellar initial mass function (IMF) and its relation with the core mass function (CMF) are actively debated issues with important implications in astrophysics. Recent ...observations in the W43 molecular complex of top-heavy CMFs, with an excess of high-mass cores compared to the canonical mass distribution, raise questions about our understanding of the star formation processes and their evolution in space and time.
Aims.
We aim to compare populations of protostellar and prestellar cores in three regions imaged in the ALMA-IMF Large Program.
Methods.
We created an homogeneous core catalogue in W43, combining a new core extraction in W43-MM1 with the catalogue of W43-MM2&MM3 presented in a previous work. Our detailed search for protostellar outflows enabled us to identify between 23 and 30 protostellar cores out of 127 cores in W43-MM1 and between 42 and 51 protostellar cores out of 205 cores in W43-MM2&MM3. Cores with neither outflows nor hot core emission are classified as prestellar candidates.
Results.
We found a similar fraction of cores which are protostellar in the two regions, about 35%. This fraction strongly varies in mass, from
f
pro
≃ 15–20% at low mass, between 0.8 and 3
M
⊙
up to
f
pro
≃ 80% above 16
M
⊙
. Protostellar cores are found to be, on average, more massive and smaller in size than prestellar cores. Our analysis also revealed that the high-mass slope of the prestellar CMF in W43,
α
= -1.46
-0.19
+0.12
, is consistent with the Salpeter slope, and thus the top-heavy form measured for the global CMF,
α
= −0.96 ± 0.09, is due to the protostellar core population.
Conclusions.
Our results could be explained by ‘clump-fed’ models in which cores grow in mass, especially during the protostellar phase, through inflow from their environment. The difference between the slopes of the prestellar and protostellar CMFs moreover implies that high-mass cores grow more in mass than low-mass cores.
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