scholarly journals VLA Observations of Nine Extended Green Objects in the Milky Way: Ubiquitous Weak, Compact Continuum Emission, and Multi-epoch Emission from Methanol, Water, and Ammonia Masers

2021 ◽  
Vol 923 (2) ◽  
pp. 263
Author(s):  
A. P. M. Towner ◽  
C. L. Brogan ◽  
T. R. Hunter ◽  
C. J. Cyganowski
Keyword(s):  
Milky Way ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Large Array ◽  
Spectral Indices ◽  
Physical Processes ◽  
Stellar Objects ◽  
Maser Emission ◽  
Very Large Array

Abstract We have observed a sample of nine Extended Green Objects (EGOs) at 1.3 and 5 cm with the Very Large Array (VLA) with subarcsecond resolution and ∼7–14 μJy beam−1-sensitivities in order to characterize centimeter continuum emission as it first appears in these massive protoclusters. We find an EGO-associated continu um emission—within 1″ of the extended 4.5 μm emission—in every field, which is typically faint (order 101–102 μJy) and compact (unresolved at 0″.3–0″.5). The derived spectral indices of our 36 total detections are consistent with a wide array of physical processes, including both non-thermal (19% of detections) and thermal free–free processes (e.g., ionized jets and compact H ii regions, 78% of sample) and warm dust (1 source). We also find an EGO-associated 6.7 GHz CH3OH and 22 GHz H2O maser emission in 100% of the sample and a NH3 (3,3) masers in ∼45%; we do not detect any NH3 (6,6) masers at ∼5.6 mJy beam−1 sensitivity. We find statistically-significant correlations between L radio and L bol at two physical scales and three frequencies, consistent with thermal emission from ionized jets, but no correlation between L H 2 O and L radio for our sample. From these data, we conclude that EGOs likely host multiple different centimeter continuum-producing processes simultaneously. Additionally, at our ∼1000 au resolution, we find that all EGOs except G18.89−0.47 contain 1 ∼ 2 massive sources based on the presence of CH3OH maser groups, which is consistent with our previous work suggesting that these are typical massive protoclusters, in which only one to a few of the young stellar objects are massive.

scholarly journals Early results from a diagnostic 1.3 cm survey of massive young protostars

2012 ◽  
Vol 8 (S287) ◽  
pp. 497-501
Author(s):  
Crystal L. Brogan ◽  
Todd R. Hunter ◽  
Claudia J. Cyganowski ◽  
Remy Indebetouw ◽  
Rachel Friesen ◽  
...  
Keyword(s):  
Massive Star ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Large Array ◽  
Stellar Objects ◽  
Very Large Array ◽  
Early Results ◽  
Wide Range ◽  
First Time ◽  
24 Ghz

AbstractWe have used the recently-upgraded Karl G. Jansky Very Large Array (JVLA) to conduct a K-band (~24 GHz) study of 22 massive young stellar objects in 1.3 cm continuum and a comprehensive set of diagnostic lines. This survey is unique in that it samples a wide range of massive star formation signposts simultaneously for the first time. In this proceeding we present preliminary results for the 11 sources in the 2-4 kpc distance bin. We detect compact NH3 cores in all of the fields, with many showing emission up through the (6,6) transition. Maser emission in the 25 GHz CH3OH ladder is present in 7 of 11 sources. We also detect non-thermal emission in the NH3 (3,3) transition in 7 of 11 sources.

Water Maser Survey toward Low‐Mass Young Stellar Objects in the Northern Sky with the Nobeyama 45 Meter Telescope and the Very Large Array

2003 ◽  
Vol 144 (1) ◽  
pp. 71-134 ◽  
Author(s):  
Ray S. Furuya ◽  
Yoshimi Kitamura ◽  
Alwyn Wootten ◽  
Mark J. Claussen ◽  
Ryohei Kawabe
Keyword(s):  
Young Stellar Objects ◽  
Large Array ◽  
Stellar Objects ◽  
Very Large Array ◽  
Low Mass ◽  
Water Maser

scholarly journals VLA cm-wave survey of young stellar objects in the Oph A cluster: constraining extreme UV- and X-ray-driven disk photoevaporation

2019 ◽  
Vol 631 ◽  
pp. A58 ◽  
Author(s):  
A. Coutens ◽  
H. B. Liu ◽  
I. Jiménez-Serra ◽  
T. L. Bourke ◽  
J. Forbrich ◽  
...  
Keyword(s):  
Dust Emission ◽  
Class Ii ◽  
Field Of View ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Class Iii ◽  
Stellar Objects ◽  
Very Large Array ◽  
X Ray ◽  
Extreme Uv

Observations of young stellar objects (YSOs) in centimeter bands can probe the continuum emission from growing dust grains, ionized winds, and magnetospheric activity that are intimately connected to the evolution of protoplanetary disks and the formation of planets. We carried out sensitive continuum observations toward the Ophiuchus A star-forming region, using the Karl G. Jansky Very Large Array (VLA) at 10 GHz over a field-of-view of 6′ and with a spatial resolution of θmaj ×θmin ~ 0.′′4 × 0.′′2. We achieved a 5 μJy beam−1 rms noise level at the center of our mosaic field of view. Among the 18 sources we detected, 16 were YSOs (three Class 0, five Class I, six Class II, and two Class III) and two were extragalactic candidates. We find that thermal dust emission generally contributed less than 30% of the emission at 10 GHz. The radio emission is dominated by other types of emission, such as gyro-synchrotron radiation from active magnetospheres, free–free emission from thermal jets, free–free emission from the outflowing photoevaporated disk material, and synchrotron emission from accelerated cosmic-rays in jet or protostellar surface shocks. These different types of emission could not be clearly disentangled. Our non-detections for Class II/III disks suggest that extreme UV-driven photoevaporation is insufficient to explain disk dispersal, assuming that the contribution of UV photoevaporating stellar winds to radio flux does not evolve over time. The sensitivity of our data cannot exclude photoevaporation due to the role of X-ray photons as an efficient mechanism for disk dispersal. Deeper surveys using the Square Kilometre Array (SKA) will have the capacity to provide significant constraints to disk photoevaporation.

The IGRINS YSO Survey II: Veiling Spectra of Pre-main-sequence Stars in Taurus-Auriga

2021 ◽  
Vol 922 (1) ◽  
pp. 27
Author(s):  
Benjamin Kidder ◽  
Gregory Mace ◽  
Ricardo López-Valdivia ◽  
Kimberly Sokal ◽  
Victoria E. Catlett ◽  
...  
Keyword(s):  
Near Infrared ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Class Iii ◽  
Infrared Excess ◽  
Stellar Objects ◽  
Star Forming ◽  
Infrared Spectrometer ◽  
Low Mass

Abstract We present measurements of the H- and K-band veiling for 141 young stellar objects (YSOs) in the Taurus-Auriga star-forming region using high-resolution spectra from the Immersion Grating Near-Infrared Spectrometer. In addition to providing measurements of r H and r K , we produce low-resolution spectra of the excess emission across the H and K bands. We fit temperatures to the excess spectra of 46 members of our sample and measure near-infrared excess temperatures ranging from 1200–2200 K, with an average of 1575 ± 225 K. We compare the luminosity of the excess continuum emission in Class II and Class III YSOs and find that a number of Class III sources display a significant amount of excess flux in the near-infrared. We conclude that the mid-infrared SED slope, and therefore young stellar object classification, is a poor predictor of the amount of near-infrared veiling. If the veiling arises in thermal emission from dust, its presence implies a significant amount of remaining inner-disk (<1 au) material in these Class III sources. We also discuss the possibility that the veiling effects could result from massive photospheric spots, unresolved binary companions, or accretion emission. Six low-mass members of our sample contain a prominent feature in their H-band excess spectra that is consistent with veiling from cool photospheric spots.

scholarly journals Inferring (sub)millimetre dust opacities and temperature structure in edge-on protostellar discs from resolved multiwavelength continuum observations: the case of the HH 212 disc

2020 ◽  
Vol 501 (1) ◽  
pp. 1316-1335
Author(s):  
Zhe-Yu Daniel Lin ◽  
Chin-Fei Lee ◽  
Zhi-Yun Li ◽  
John J Tobin ◽  
Neal J Turner
Keyword(s):  
Major Axis ◽  
Outer Edge ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Temperature Structure ◽  
Stellar Objects ◽  
High Resolution Data ◽  
Very Large Array ◽  
Gravitational Stability ◽  
Protostellar Discs

ABSTRACT (Sub)millimetre dust opacities are required for converting the observable dust continuum emission to the mass, but their values have long been uncertain, especially in discs around young stellar objects. We propose a method to constrain the opacity κν in edge-on discs from a characteristic optical depth τ0,ν, the density ρ0, and radius R0 at the disc outer edge through κν = τ0,ν/(ρ0R0), where τ0,ν is inferred from the shape of the observed flux along the major axis, ρ0 from gravitational stability considerations, and R0 from direct imaging. We applied the 1D semi-analytical model to the embedded, Class 0, HH 212 disc, which has high-resolution data in Atacama Large Millimetre/submillimetre Array (ALMA) bands 9, 7, 6, and 3 and Very Large Array Ka band (λ = 0.43, 0.85, 1.3, 2.9, and 9.1 mm). The modelling is extended to 2D through RADMC-3D radiative transfer calculations. We find a dust opacity of κν ≈ 1.9 × 10−2, 1.3 × 10−2, and 4.9 × 10−3 cm2 g−1 of gas and dust for ALMA bands 7, 6, and 3, respectively, with uncertainties dependent on the adopted stellar mass. The inferred opacities lend support to the widely used prescription κλ = 2.3 × 10−2(1.3mm/λ) cm2 g−1 . We inferred a temperature of ∼45 K at the disc outer edge that increases radially inwards. It is well above the sublimation temperatures of ices such as CO and N2, which supports the notion that the disc chemistry cannot be completely inherited from the protostellar envelope.

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

scholarly journals Class I methanol masers in the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 147-149
Author(s):  
L. O. Sjouwerman ◽  
Y. M. Pihlström
Keyword(s):  
Galactic Center ◽  
Class I ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Sagittarius A ◽  
Current Location ◽  
Theoretical Predictions ◽  
Methanol Masers ◽  
Sgr A

AbstractWe report on the detection of 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) complex with the Karl G. Jansky Very Large Array (VLA). These VLA observations show that the Sgr A complex harbors at least three different maser tracers of shocked regions in the radio regime. The 44 GHz masers correlate with the positions and velocities of previously detected 36 GHz CH3OH masers, but less with 1720 MHz OH masers. Our detections agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under even cooler and less dense conditions. We speculate that the geometry of the 36 GHz masers outlines the current location of a shock front.

scholarly journals Quasi-simultaneous Radio/X-Ray Observations of the Candidate Transitional Millisecond Pulsar 3FGL J1544.6−1125 during its Low-luminosity Accretion-disk State

2021 ◽  
Vol 923 (1) ◽  
pp. 3
Author(s):  
Amruta D. Jaodand ◽  
Adam T. Deller ◽  
Nina Gusinskaia ◽  
Jason W. T. Hessels ◽  
James C. A. Miller-Jones ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Array ◽  
Millisecond Pulsar ◽  
Very Large Array ◽  
X Ray ◽  
Upper Limit ◽  
5 Ghz ◽  
Variable Radio

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

scholarly journals NIKA2 observations around LBV stars Emission from stars and circumstellar material

2020 ◽  
Vol 228 ◽  
pp. 00023
Author(s):  
J. Ricardo Rizzo ◽  
Alessia Ritacco ◽  
Cristobal Bordiu
Keyword(s):  
Thermal Emission ◽  
Continuum Emission ◽  
Core Collapse ◽  
Spectral Indices ◽  
Ionized Gas ◽  
Dark Cloud ◽  
High Frequencies ◽  
Circumstellar Material ◽  
Dark Clouds ◽  
Luminous Blue Variable

Luminous Blue Variable (LBV) stars are evolved massive objects, previous to core-collapse supernova. LBVs are characterized by photometric and spectroscopic variability, produced by strong and dense winds, mass-loss events and very intense UV radiation. LBVs strongly disturb their surroundings by heating and shocking, and produce important amounts of dust. The study of the circumstellar material is therefore crucial to understand how these massive stars evolve, and also to characterize their effects onto the interstellar medium. The versatility of NIKA2 is a key in providing simultaneous observations of both the stellar continuum and the extended, circumstellar contribution. The NIKA2 frequencies (150 and 260 GHz) are in the range where thermal dust and free-free emission compete, and hence NIKA2 has the capacity to provide key information about the spatial distribution of circumstellar ionized gas, warm dust and nearby dark clouds; non-thermal emission is also possible even at these high frequencies. We show the results of the first NIKA2 survey towards five LBVs. We detected emission from four stars, three of them immersed in tenuous circumstellar material. The spectral indices show a complex distribution and allowed us to separate and characterize different components. We also found nearby dark clouds, with spectral indices typical of thermal emission from dust. Spectral indices of the detected stars are negative and hard to be explained only by free-free processes. In one of the sources, G79.29+0.46, we also found a strong correlation of the 1mm and 2mm continuum emission with respect to nested molecular shells at ≈1 pc from the LBV. The spectral index in this region clearly separates four components: the LBV star, a bubble characterized by free-free emission, and a shell interacting with a nearby infrared dark cloud.

Sign in / Sign up

Export Citation Format

Share Document