Submillimeter and Mid-Infrared Variability of Young Stellar Objects in the M17SWex Intermediate-Mass Star-Forming Region
Geumsook Park, Doug Johnstone, Carlos Contreras Pena, Jeong-Eun Lee, Sheng-Yuan Liu, Gregory Herczeg, Steve Mairs, Zhiwei Chen, Jennifer Hatchell, Kee-Tae Kim, … 展开作者
Geumsook Park, Doug Johnstone, Carlos Contreras Pena, Jeong-Eun Lee, Sheng-Yuan Liu, Gregory Herczeg, Steve Mairs, Zhiwei Chen, Jennifer Hatchell, Kee-Tae Kim, Mi-Ryang Kim, Keping Qiu, Yao-Te Wang, Xu Zhang, The JCMT Transient Team
备注：
Accepted for Publication in The Astronomical Journal
We present a comprehensive analysis of young stellar object (YSO) variability within the M17 Southwest Extension (M17 SWex), using 3.5 years of monitoring data from the JCMT Transient Survey at sub-millimeter (sub-mm) and 9 years from the NEOWISE mission at mid-infrared (mid-IR). Our study encompasses observations of 147 bright sub-mm peaks identified within our deep JCMT co-added map as well as 156 YSOs in NEOWISE W1 and 179 in W2 that were previously identified in Spitzer surveys. We find three robust sub-mm variables: two are candidate YSOs and one is a likely extragalactic source. At mid-IR wavelengths, our analysis reveals secular and stochastic variability in 47 YSOs, with the highest fraction of secular variability occurring at the earliest evolutionary stage. This is similar to what has previously been observed for low-mass YSO variability within the Gould Belt. However, we observe less overall variability in M17SWex at both the sub-mm and mid-IR. We suspect that this lower fraction is due to the greater distance to M17 SWex. Our findings showcase the utility of multi-wavelength observations to better capture the complex variability phenomena inherent to star formation processes and demonstrate the importance of years-long monitoring of a diverse selection of star-forming environments.
Formation processes of high-mass stars have been long-standing issues in astronomy and astrophysics. This is mainly because of major difficulties in observational studies such as a smaller number of high-mass young stellar objects (YSOs), larger distances, and more complex structures in young high-mass clusters compared with nearby low-mass isolated star-forming regions (SFRs), and extremely large opacity of interstellar dust except for centimeter to submillimeter wavelengths. High resolution and high sensitivity observations with Atacama Large Millimeter/Submillimeter Array (ALMA) at millimet…
A two-parameter semi-empirical model is presented for the spectral energy distributions of galaxies with contributions to their infrared-submillimeter-radio emission from both star formation and accretion disk-powered activity. This model builds upon a previous one-parameter family of models for star-forming galaxies, and includes an update to the mid-infrared emission using an average template obtained from Spitzer Space Telescope observations of normal galaxies. Star-forming/AGN diagnostics based on PAH equivalent widths and broadband infrared colors are presented, and example mid-infrared A…
We report the discovery of an extremely young protostar, SMM11, located in the associated submillimeter condensation SMM11 in the Serpens Main cluster using the Atacama Large Millimeter/submillimeter Array (ALMA) during its Cycle 3 at 1.3 mm and an angular resolution of ~0.5"~210 AU. SMM11 is a Class 0 protostar without any counterpart at 70 um or shorter wavelengths. The ALMA observations show 1.3 mm continuum emission associated with a collimated 12CO bipolar outflow. Spitzer and Herschel data show that SMM11 is extremely cold (T_bol=26 K) and faint (L_bol<~0.9 Lsun). We estimate the inclina…
We used the Spitzer Infrared Spectrograph (IRS) to study the mid-IR properties and investigate the energetics of 24 Submillimeter Galaxies (SMGs). This is the largest sample of SMGs observed with Spitzer IRS and covers the full extent of properties of the radio-identified population of SMGs in the redshift range of z ~ 0.65-3.2. We observe broad emission features from Polycyclic Aromatic Hydrocarbons (PAHs) in more than 80% of our sample. We find that the median mid-IR spectrum is well described by a starburst component with an additional power law, Fnu ~ nu^-2, likely representing a < 32% AGN…
Spitzer IRAC observations and stellar photometric catalogs are presented for the Massive Young Star-Forming Complex Study in the Infrared and X-ray (MYStIX). MYStIX is a multiwavelength census of young stellar members of twenty nearby (d < 4 kpc), Galactic, star-forming regions that contain at least one O star. All regions have data available from the Spitzer Space Telescope, consisting of GLIMPSE or other published catalogs for eleven regions and results of our own photometric analysis of archival data for the remaining nine regions. This paper seeks to construct deep and reliable catalogs of…
Temporal photometric variations at near infrared to submillimeter wavelengths have been found in low-mass young stellar objects. These phenomena are generally interpreted as accretion events of star-disk systems with varying accretion rates. There is growing evidence suggesting that similar luminosity flaring also occurs in high-mass star/cluster-forming regions. We report in this Letter the rise and fall of the 900 $μ$m continuum emission and the newly found 349.1 GHz methanol maser emission in the massive star forming region S255IR~SMA1 observed with the Submillimeter Array and the Atacama L…
The presence of crystalline silicates has been detected in the circumstellar environment of several young stars in the recent past and there is evidence of silicon carbide (SiC) detection in the envelope of pre-main sequence star SVS13. In this work, we have attempted to probe the presence of SiC in the dust around protoplanetary disks in a sample of young stars. We have modelled the linear polarization of composite dust grains in the mid-infrared (MIR: 8--13 $μ$m) using silicates as the host with various inclusions of SiC and graphites using the Discrete Dipole Approximation (DDA) and the Eff…
We systematically investigate the mid-infrared (MIR; $λ>3 ~μ$m) time variability of uniformly selected $\sim800$ massive young stellar objects (MYSOs) from the Red MSX Source (RMS) survey. Out of the 806 sources, we obtain reliable 9-year-long MIR magnitude variability data of 331 sources at the 3.4~$μ$m (W1) and 4.6~$μ$m (W2) bands by cross-matching the MYSO positions with ALLWISE and NEOWISE catalogs. After applying the variability selections using ALLWISE data, we identify 5 MIR-variable candidates. The light curves show various classes, with the periodic, plateau-like, and dipper features.…
We report the study of far-IR sizes of submillimeter galaxies (SMGs) in relation to their dust-obscured star formation rate (SFR) and active galactic nuclei (AGN) presence, determined using mid-IR photometry. We determined the millimeter-wave ($λ_{\rm obs}=1100 μ$m) sizes of 69 ALMA-identified SMGs, selected with $\geq10$$σ$ confidence on ALMA images ($F_{\rm 1100 μm}=1.7$--7.4 mJy). We found that all the SMGs are located above an avoidance region in the millimeter size-flux plane, as expected by the Eddington limit for star formation. In order to understand what drives the different millimete…
The early evolutionary stage of brown dwarfs are not very well characterized, specially during the embedded phase. To gain insight into the dominant formation mechanism of very low-mass objects and brown dwarfs, we conducted deep observations at 870$μ$m with the LABOCA bolometer at the APEX telescope. Our goal was to identify young sub-mm sources in the Barnard 30 dark cloud. We complemented these data with multi-wavelength observations from the optical to the far-IR and. As a result, we have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members withi…
Based on the molecular emission in the $^{12}$CO(2-1) and $^{13}$CO(2-1) lines, and the continuum emission in the MIR and FIR towards the S21 IR dust bubble, we analyze the physical characteristics of the gas and dust linked to the nebula and the presence of young stellar objects (YSOs) in its environs. The line emission reveals a clumpy molecular shell, 1.4 pc in radius, encircling S21. The total molecular mass in the shell amounts to 2900 solar masses and the original ambient density, 2.1 x 10$^3$ cm$^{-3}$, indicating that the bubble is evolving in a high density interstellar medium. The im…
We present our results from a mid-infrared interferometric survey targeted at the planet-forming region in the circumstellar disks around low- and intermediate-mass young stars. Our sample consist of 82 objects, including T Tauri stars, Herbig Ae stars, and young eruptive stars. Our main results are: 1) Disks around T Tauri stars are similar to those around Herbig Ae stars, but are relatively more extended once we account for stellar luminosity. 2) From the distribution of the sizes of the mid-infrared emitting region we find that inner dusty disk holes may be present in roughly half of the sa…
G79.3+0.3 is an infrared dark cloud in the Cygnus-X complex that is home to massive deeply embedded young stellar objects (YSOs). We have produced a submillimeter array (SMA) 1.3 mm continuum image and $^{12}$CO line maps of the eastern section of G79.3+0.3 in which we detect five separate YSOs. We have estimated physical parameters for these five YSOs and others in the vicinity of G79.3+0.3 by fitting existing photometry from Spitzer, Herschel, and ground-based telescopes to spectral energy distribution models. Through these model fits we find that the most massive YSOs seen in the SMA 1.3mm …
Young massive stars in the center of crowded star clusters are expected to undergo close dynamical encounters that could lead to energetic, explosive events. However, there has so far never been clear observational evidence of such a remarkable phenomenon. We here report new interferometric observations made with the Submillimeter Array (SMA) that indicate the well known enigmatic wide-angle outflow located in the Orion BN/KL star-forming region to have been produced by such a violent explosion during the disruption of a massive young stellar system, and that this was caused by a close dynamic…
A giant molecular cloud has been detected surrounding the supernebula in NGC 5253, revealing details of the formation and feedback process in a very massive star cluster. "Cloud D" was recently mapped in CO J=3-2 with the Submillimeter Array. The cloud surrounds a currently forming massive cluster of mass ~10$^6$ $\rm M_\odot$ and luminosity ~10$^9$ $\rm L_\odot$. Cloud D is hot, clearly associated with the cluster, yet kinematically relatively quiescent. The dust mass is ~15,000 $\rm M_\odot$, giving a gas-to-dust ratio of ~50, nearly an order of magnitude lower than expected for this low met…
We present spatial and kinematic correlation between the young stellar population and the cloud clumps in the Ophiuchus star-forming region. The stellar sample consists of known young objects at various evolutionary stages, taken from the literature, some of which are diagnosed with Gaia EDR3 parallax and proper-motion measurements. The molecular gas is traced by the 850 $μ$m Submillimetre Common-User Bolometer Array-2 image, reaching $\sim$2.3 mJy beam$^{-1}$, the deepest so far for the region, stacked from the James Clerk Maxwell Telescope/Transient program aiming to detect submillimeter out…
We present the discovery of the simultaneous flux variation of a massive young stellar object (MYSO) G036.70+00.09 (G036.70) both in the maser emission and mid-infrared (MIR;$λ=3$--$5$~$μ$m) bands. Utilizing the ALLWISE and NEOWISE archival databases covering a long time span of approximately 10 years with a cadence of 6 months, we confirmed that G036.70 indicates a stochastic year-long MIR variability with no signs of the WISE band color change of W1 (3.4~$μ$m) $-$W2 (4.6~$μ$m). Cross-matching the MIR data set with the high-cadence 6.7~GHz class II methanol maser flux using a Hitachi 32-m rad…
We report detections of two candidate distant submillimeter galaxies (SMGs), MM J154506.4$-$344318 and MM J154132.7$-$350320, which are discovered in the AzTEC/ASTE 1.1 mm survey toward the Lupus-I star-forming region. The two objects have 1.1 mm flux densities of 43.9 and 27.1 mJy, and have Herschel/SPIRE counterparts as well. The Submillimeter Array counterpart to the former SMG is identified at 890 $μ$m and 1.3 mm. Photometric redshift estimates using all available data from the mid-infrared to the radio suggest that the redshifts of the two SMGs are $z_{\rm photo} \simeq$ 4-5 and 3, respec…
We present high resolution (R = 75,000-100,000) mid-infrared spectra of the high-mass embedded young star IRS 1 in the NGC 7538 star-forming region. Absorption lines from many rotational states of C2H2, 13C12CH2, CH3, CH4, NH3, HCN, HNCO, and CS are seen. The gas temperature, column density, covering factor, line width, and Doppler shift for each molecule are derived. All molecules were fit with two velocity components between -54 and -63 km/s. We find high column densities (~ 10e16 cm^2) for all the observed molecules compared to values previously reported and present new results for CH3 and …
[abridged] Our knowledge of the inner structure of embedded massive young stellar objects is still quite limited. We attempt here to overcome the spatial resolution limitations of conventional thermal infrared imaging. We employed mid-infrared interferometry using the MIDI instrument on the ESO/VLTI facility to investigate M8E-IR, a well-known massive young stellar object suspected of containing a circumstellar disk. Spectrally dispersed visibilities in the 8-13 micron range were obtained at seven interferometric baselines. We resolve the mid-infrared emission of M8E-IR and find typical sizes …
We apply mid-infrared spectro-interferometry to the massive young stellar object CRL2136. The observations were performed with the Very Large Telescope Interferometer and the MIDI instrument at a 42m baseline probing angular scales of 50 milli-arcseconds. We model the observed visibilities in parallel with diffraction-limited images at both 24.5micron and in the N-band (with resolutions of 0.6" and 0.3", respectively), as well as the spectral energy distribution. The arcsec-scale spatial information reveals the well-resolved emission from the dusty envelope. By simultaneously modelling the spa…
Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observatio…
Recent mid-infrared observations of young stellar objects have found significant variations possibly indicative of changes in the structure of the circumstellar disk. Previous models of this variability have been restricted to axisymmetric perturbations in the disk. We consider simple models of a non-axisymmetric variation in the inner disk, such as a warp or a spiral wave. We find that the precession of these non-axisymmetric structures produce negligible flux variations but a change in the height of these structures can lead to significant changes in the mid-infrared flux. Applying these mod…
We report the results of visual spectroscopy, mid-infrared (MIR) mapping and photometry, and near-infrared photometry of two candidate symbiotic stars (IPHAS J193108.67+164950.5 and IPHAS J193709.65+202655.7) associated with extended MIR emission. Our analysis of the continua of these sources shows that they are likely to represent Class I-II young stellar objects (YSOs) in which most of the IR emission arises from circumstellar discs, and for which the physical characteristics (stellar temperatures, radii, masses and luminosities) are similar. The extended emission is characterized by a subst…
We present results from Submillimeter Array (SMA) 860-micron sub-arcsec astrometry and multiwavelength observations of the brightest millimeter (S_1.1mm = 8.4 mJy) source, SSA22-AzTEC1, found near the core of the SSA22 protocluster that is traced by Lyαemitting galaxies at z = 3.09. We identify a 860-micron counterpart with a flux density of S_860um = 12.2 +/- 2.3 mJy and absolute positional accuracy that is better than 0.3". At the SMA position, we find radio to mid-infrared counterparts, whilst no object is found in Subaru optical and near-infrared deep images at wavelengths \le 1 micron (J …
We present 168 arcmin^2 spectral images of the Sgr B2 complex taken with Herschel/SPIRE-FTS. We detect ubiquitous emission from CO (up to J=12-11), H2O, [CI]492, 809 GHz, and [NII] 205 um lines. We also present maps of the SiO, N2H+, HCN, and HCO+ emission obtained with the IRAM30m telescope. The cloud environment dominates the emitted FIR (80%), H2O 752 GHz (60 %) mid-J CO (91%), and [CI] (93 %) luminosity. The region shows very extended [NII] emission (spatially correlated with the 24 and 70 um dust emission). The observed FIR luminosities imply G_0~10^3. The extended [CI] emission arises fr…
The central structure in three of the brightest unlensed z=3-4 submillimeter galaxies are investigated through 0.015" - 0.05" (120 -- 360~pc) 860 micron continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kpc in AzTEC1 and AzTEC8 are extremely complex, and they are composed of multiple ~200 pc clumps. AzTEC4 consists of two sources that are separated by ~1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ~300 - 3000 Msun/yr/kpc^2, suggesting regions with extreme star forma…
We present mid-infrared (MIR) observations, made with the TIMMI2 camera on the ESO 3.6 m telescope, toward 14 young massive star-forming regions. All regions were imaged in the N band, and nine in the Q band, with an angular resolution of ~ 1 arcsec. Typically, the regions exhibit a single or two compact sources (with sizes in the range 0.008-0.18 pc) plus extended diffuse emission. The Spitzer-Galactic Legacy Infrared Mid-Plane Survey Extraordinaire images of these regions show much more extended emission than that seen by TIMMI2, and this is attributed to polycyclic aromatic hydrocarbon (PAH…
We present line and continuum observations (resolution ~0.3"-3.5") made with the Atacama Large Millimeter/submillimeter Array (ALMA), Submillimeter Array, and Very Large Array of a young O-type protostar W42-MME (mass: 19-4 Msun). The ALMA 1.35 mm continuum map (resolution ~1") shows that W42-MME is embedded in one of the cores (i.e., MM1) located within a thermally supercritical filament-like feature (extent ~0.15 pc) containing three cores (mass ~1-4.4 Msun). Several dense/hot gas tracers are detected toward MM1, suggesting the presence of a hot molecular core with the gas temperature of ~38…
We use two 4.5micron Spitzer (IRAC) maps of the NGC 1333 region taken over approx. 7 yr interval to determine proper motions of its associated outflows. This is a first, successful attempt at obtaining proper motions of stellars outflow from Spitzer observations. For the outflow formed by the Herbig-Haro objects HH7, 8 and 10, we find proper motions of approx. 9-13 km/s, which are consistent with previously determined optical proper motions of these objects. We determine proper motions for a total of 8 outflows, ranging from approx. 10 to 100 km/s. The derived proper motions show that out of t…
We use SCUBA 850 micron and CO observations to analyze the surroundings of three Galactic ring-like HII regions, KR 7, KR 81, and KR 120 (Sh 2-124, Sh 2-165 and Sh 2-187), with the aim of finding sites of triggered star formation. We find one prominent submillimeter (sub-mm) source for each region, located at the interface between the HII region and its neutral surroundings. Using Two Micron All Sky Survey photometry, we find that the prominent sub-mm source for KR 120 probably contains an embedded cluster of young stellar objects (YSOs), making it a likely site for triggered star formation. T…
We present a survey of the Orion A and B molecular clouds undertaken with the IRAC and MIPS instruments onboard Spitzer. In total, five distinct fields were mapped covering 9 sq. degrees in five mid-IR bands spanning 3-24 microns. The survey includes the Orion Nebula Cluster, the Lynds 1641, 1630 and 1622 dark clouds, and the NGC 2023, 2024, 2068 and 2071 nebulae. These data are merged with the 2MASS point source catalog to generate a catalog of eight band photometry. We identify 3479 dusty young stellar objects (YSOs) in the Orion molecular clouds by searching for point sources with mid-IR co…
In this paper we present our imaging observations on the CO(7-6) line and its underlying continuum emission of the young submillimeter galaxy LESS 073 at redshift 4.755, using the Atacama Large Millimeter/submillimeter Array (ALMA). At the achieved resolution of $\sim$$1^{\prime\prime}.2\times0^{\prime\prime}.9$ ($8\times6$~kpc$^2$), the CO(7-6) emission is largely unresolved (with a deconvolved size of $1^{\prime\prime}.1(\pm0^{\prime\prime}.5) \times 0^{\prime\prime}.9(\pm0^{\prime\prime}.8)$), and the continuum emission is totally unresolved. The CO(7-6) line emission has an integrated flux…
We present a multiwavelength investigation of star formation activity towards the southern H II regions associated with IRAS 17160-3707, located at a distance of 6.2 kpc with a bolometric luminosity of 830000 Lsun.The ionised gas distribution and dust clumps in the parental molecular cloud are examined in detail using measurements at infrared, submillimeter and radio wavelengths.The radio continuum images at 1280 and 610 MHz obtained using Giant Metrewave Radio Telescope reveal the presence of multiple compact sources as well as nebulous emission.At submillimeter wavelengths, we identify seven…
Based on observations with the IRAM 30-m and Yebes 40-m telescopes, we report evidence of the detection of Milky Way-like, low-excitation molecular gas, up to the transition CO($J=5-4$), in a distant, dusty star-forming galaxy at $z_{CO}=1.60454$. WISE J122651.0+214958.8 (alias SDSSJ1226, the Cosmic Seahorse), is strongly lensed by a foreground galaxy cluster at $z=0.44$ with a source magnification of $μ=9.5\pm0.7$. This galaxy was selected by cross-correlating near-to-mid infrared colours within the full-sky AllWISE survey, originally aiming to discover rare analogs of the archetypical strong…
Massive star formation occurs in the interior of giant molecular clouds (GMC) and proceeds through many stages. In this work, we focus on massive young stellar objects (MYSOs) and Ultra-Compact HII regions (UCHII), where the former are enshrouded in dense envelopes of dust and gas, which the latter have begun dispersing. By selecting a complete sample of MYSOs and UCHII from the Red MSX Source (RMS) survey data base, we combine Planck and IRAS data and build their Spectral Energy Distributions (SEDs). With these, we estimate the physical properties (dust temperatures, mass, luminosity) of the …
In 2019, Sgr A* - the supermassive black hole in the Galactic Center - underwent unprecedented flaring activity in the near infrared (NIR), brightening by up to a factor of 100 compared to quiescent values. Here we report ALMA observations of Sgr A*'s continuum variability at 1.3 mm (230 GHz) - a tracer of the accretion rate - conducted one month after the brightest detected NIR flare and in the middle of the flaring activity of 2019. We develop an innovative light curve extraction technique which (together with ALMA's excellent sensitivity) allows us to obtain the light curves which are simul…
Torsionally excited methanol in massive young stellar objects: The role of the mid-IR radiation field
Università degli Studi di Cagliari（卡利亚里大学）；INAF - Osservatorio Astronomico di Cagliari（意大利国家天体物理研究所卡利亚里天文台）；INAF - Istituto di Radioastronomia di Bologna（意大利国家天体物理研究所博洛无线电天文研究所）；INAF - Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所天体物理学与行星科学研究所）；Alma Mater Studiorum – Università di Bologna（博洛尼亚大学）；INAF-Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Centre for Astrophysics and Planetary Science, University of Kent（肯特大学天体物理学与行星科学中心）；Haystack Observatory, Massachusetts Institute of Technology（麻省理工学院海斯塔克天文台）；European Southern Observatory（欧洲南方天文台）；Osservatorio Astronomico di Brera（布雷拉天文台）
We present sub-arcsecond resolution HCN (4-3) and CO (3-2) observations made with the Submillimeter Array (SMA), toward an extremely young intermediate-mass protostellar core, MMS 6-main, located in the Orion Molecular Cloud 3 region (OMC-3). We have successfully imaged a compact molecular outflow lobe (~1500 AU) associated with MMS6-main, which is also the smallest molecular outflow ever found in the intermediate-mass protostellar cores. The dynamical time scale of this outflow is estimated to be <100 yr. The line width dramatically increases downstream at the end of the molecular outflow (Δv…
We present the results from a 1.1 mm imaging survey of the SSA22 field, known for having an overdensity of z=3.1 Lyman-alpha emitting galaxies (LAEs), taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE). We imaged a 950 arcmin$^2$ field down to a 1 sigma sensitivity of 0.7-1.3 mJy/beam to find 125 submillimeter galaxies (SMGs) with a signal to noise ratio >= 3.5. Counterpart identification using radio and near/mid-infrared data was performed and one or more counterpart candidates were found for 59 SMGs. Photometric redshifts based on optical to near-infrared im…
We present a systematic analysis of the mid-infrared (MIR) properties of the youngest radio galaxies, based on low-resolution data provided by the {\it WISE} and {\it IRAS} satellites. We restrict our analysis to sources with available X-ray data that constitute the earliest phase of radio galaxy evolution, i.e. those classified as Gigahertz Peaked Spectrum (GPS) and/or Compact Symmetric Objects (CSOs). In our sample of 29 objects, we find that the host galaxies are predominantly red/yellow ellipticals, with some of them displaying distorted morphology. We find a variety of MIR colors, and obs…
