skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Attention:

The DOI auto-population feature in the Public Access Repository (PAR) will be unavailable from 4:00 PM ET on Tuesday, July 8 until 4:00 PM ET on Wednesday, July 9 due to scheduled maintenance. We apologize for the inconvenience caused.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Deuterium fractionation across the infrared-dark cloud G034.77−00.55 interacting with the supernova remnant W44
Context.Supernova remnants (SNRs) may regulate star formation in galaxies. For example, SNR-driven shocks may form new molecular gas or compress pre-existing clouds and trigger the formation of new stars. Aims.To test this scenario, we measured the deuteration of N2H+, DfracN2H+– a well-studied tracer of pre-stellar cores – across the infrared-dark cloud (IRDC) G034.77-00.55, which is known to be experiencing a shock interaction with the SNR W44. Methods.We use N2H+and N2D+J= 1−0 single pointing observations obtained with the 30m antenna at the Instituto de Radioas-tronomia Millimetrica to infer DfracN2H+towards five positions across the cloud, namely a massive core, different regions across the shock front, a dense clump, an+d ambient gas. Results.We find DfracN2H+in the range 0.03−0.1, which is several orders of magnitude larger than the cosmic D/H ratio (~10−5). The DfracN2H+across the shock front is enhanced by more than a factor of 2 (DfracN2H+~ 0.05 - 0.07) with respect to the ambient gas (≤0.03) and simila+r to that measured generally in pre-stellar cores. Indeed, in the massive core and dense clump regions of this IRDC we measure DfracN2H+~ 0.01. Conclusions.We find enhanced deuteration of N2H+across the region of the shock, that is, at a level that is enhanced with respect to regions of unperturbed gas. It is possible that this has been induced by shock compression, which would then be indirect evidence that the shock is triggering conditions for future star formation. However, since unperturbed dense regions also show elevated levels of deuteration, further, higher-resolution studies are needed to better understand the structure and kinematics of the deuterated material in the shock region; for example, to decipher whether it is still in a relatively diffuse form or is already organised in a population of low-mass pre-stellar cores.  more » « less
Award ID(s):
2009674
PAR ID:
10569825
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
EDP Sciences
Date Published:
Journal Name:
Astronomy & Astrophysics
Volume:
675
ISSN:
0004-6361
Page Range / eLocation ID:
A190
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    Context. We have studied the dense gas morphology and kinematics towards the infrared dark cloud (IRDC) G034.77-00.55, shock-interacting with the SNR W44, to identify evidence of early-stage star formation induced by the shock. Aims. We used high angular resolution N2H+(1−0) images across G034.77-00.55, obtained with the Atacama Large Millimeter/sub-Millimeter Array. N2H+is a well-known tracer of dense and cold material, optimal for identifying gas that has the highest potential to harbour star formation. Methods. The N2H+emission is distributed in two elongated structures, one towards the dense ridge at the edge of the source and one towards the inner cloud. Both elongations are spatially associated with well-defined mass-surface density features. The velocities of the gas in the two structures (i.e. 38–41 km s−1and 41–43 km s−1) are consistent with the lowest velocities of the J- and C-type parts, respectively, of the SNR-driven shock. A third velocity component is present at 43–45.5 km s–1. The dense gas shows a fragmented morphology with core-like fragments at scales consistent with the Jeans lengths, masses of ~1–20 M⊙, densities of (n(H2)≥105cm–3) sufficient to host star formation in free-fall timescales (a few 104yr), and with virial parameters that suggest a possible collapse. Results. The W44 driven shock may have swept up the encountered material, which is now seen as a dense ridge, almost detached from the main cloud, and an elongation within the inner cloud, well constrained in both N2H+emission and mass surface density. This shock compressed material may have then fragmented into cores that are either in a starless or pre-stellar stage. Additional observations are needed to confirm this scenario and the nature of the cores. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    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 HIIregions 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 13.2M⊙. We fitted the resulting high-mass end of the CMF with a single power law of the form N(log(M)) ∝ Mα, obtainingα= −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 HIIregions and their surroundings than in the rest of the field. We also found that the cores’ masses were rather low (maximum mass of ~13M⊙). 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 HIIregions, 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. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    Context. A large fraction of stars form in clusters containing high-mass stars, which subsequently influences the local and galaxy-wide environment. Aims. Fundamental questions about the physics responsible for fragmenting molecular parsec-scale clumps into cores of a few thousand astronomical units (au) are still open, that only a statistically significant investigation with ALMA is able to address; for instance: the identification of the dominant agents that determine the core demographics, mass, and spatial distribution as a function of the physical properties of the hosting clumps, their evolutionary stage and the different Galactic environments in which they reside. The extent to which fragmentation is driven by clumps dynamics or mass transport in filaments also remains elusive. Methods. With the ALMAGAL project, we observed the 1.38 mm continuum and lines toward more than 1000 dense clumps in our Galaxy, withM≥ 500 M⊙, Σ ≥ 0.1 g cm−2andd≤ 7.5 kiloparsec (kpc). Two different combinations of ALMA Compact Array (ACA) and 12-m array setups were used to deliver a minimum resolution of ∼1000 au over the entire sample distance range. The sample covers all evolutionary stages from infrared dark clouds (IRDCs) to H IIregions from the tip of the Galactic bar to the outskirts of the Galaxy. With a continuum sensitivity of 0.1 mJy, ALMAGAL enables a complete study of the clump-to-core fragmentation process down toM∼ 0.3 M⊙across the Galaxy. The spectral setup includes several molecular lines to trace the multiscale physics and dynamics of gas, notably CH3CN, H2CO, SiO, CH3OH, DCN, HC3N, and SO, among others. Results. We present an initial overview of the observations and the early science product and results produced in the ALMAGAL Consortium, with a first characterization of the morphological properties of the continuum emission detected above 5σin our fields. We used “perimeter-versus-area” and convex hull-versus-area metrics to classify the different morphologies. We find that more extended and morphologically complex (significantly departing from circular or generally convex) shapes are found toward clumps that are relatively more evolved and have higher surface densities. Conclusions. ALMAGAL is poised to serve as a game-changer for a number of specific issues in star formation: clump-to-core fragmentation processes, demographics of cores, core and clump gas chemistry and dynamics, infall and outflow dynamics, and disk detections. Many of these issues will be covered in the first generation of papers that closely follow on the present publication. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    The ALMA-IMF Large Program provides multi-tracer observations of 15 Galactic massive protoclusters at a matched sensitivity and spatial resolution. We focus on the dense gas kinematics of the G353.41 protocluster traced by N2H+(1−0), with a spatial resolution of ~0.02 pc. G353.41, at a distance of ~2kpc, is embedded in a larger-scale (~8 pc) filament and has a mass of ~2.5 × 103M⊙within 1.3 × 1.3 pc2. We extracted the N2H+(1−0) isolated line component and decomposed it by fitting up to three Gaussian velocity components. This allows us to identify velocity structures that are either muddled or impossible to identify in the traditional position-velocity diagram. We identify multiple velocity gradients on large (~1 pc) and small scales (~0.2pc). We find good agreement between the N2H+velocities and the previously reported DCN core velocities, suggesting that cores are kinematically coupled with the dense gas in which they form. We have measured nine converging “V-shaped” velocity gradients (VGs) (~20 km s−1pc−1) that are well resolved (sizes ~0.1 pc), mostly located in filaments, which are sometimes associated with cores near their point of convergence. We interpret these V-shapes as inflowing gas feeding the regions near cores (the immediate sites of star formation). We estimated the timescales associated with V-shapes as VG−1, and we interpret them as inflow timescales. The average inflow timescale is ~67 kyr, or about twice the free-fall time of cores in the same area (~33 kyr) but substantially shorter than protostar lifetime estimates (~0.5 Myr). We derived mass accretion rates in the range of (0.35–8.77) × 10−4M⊙yr−1. This feeding might lead to further filament collapse and the formation of new cores. We suggest that the protocluster is collapsing on large scales, but the velocity signature of collapse is slow compared to pure free-fall. Thus, these data are consistent with a comparatively slow global protocluster contraction under gravity, and faster core formation within, suggesting the formation of multiple generations of stars over the protocluster’s lifetime. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Monthly Notices of the Royal Astronomical Society)
    ABSTRACT The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2−1, HCO+J = 1−0, and HCN J = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ‘dense gas’ star formation scaling relations and massive protocluster formation. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email