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C. Carrasco-Gonzalez

Publications and source records attributed to C. Carrasco-Gonzalez.

At least 19 recordsLinked to original sources

The 10-15 GHz radio continuum survey of the Galactic Plane with SKAO

Star formation emerges from the complex interplay between gravity, turbulence, magnetic fields, and stellar feedback, all of which vary across spatial scales and Galactic environments. Over the past decades, extensive multiwavelength surveys of the Galactic Plane have progressively unveiled this complexity. Far-infrared and sub-millimetre surveys have identified and characterized tens of thousands of star-forming regions, revealing their mass, temperature, and evolutionary stage. Complementary molecular-line surveys, spanning several CO transitions and isotopologues, have mapped the gas kinematics from giant molecular clouds down to sub-parsec structures. The advent of interferometers such as ALMA has revolutionized this field, enabling systematic studies of gas dynamics, fragmentation, and collapse in dense clumps at scales of a few thousand astronomical units. At the same time, mid-infrared and radio surveys at frequencies 0.8 <= nu <= 5 GHz have traced ionised gas associated with the earliest and latest phases of massive-star evolution, including thermal radio jets, hypercompact and ultracompact HII regions, supernova remnants, planetary nebulae, and evolved massive stars. Yet, a uniform, Galaxy-wide census of ionised structures and feedback processes remains elusive. A transformational leap forward requires a sensitive, high-resolution radio survey of the Galactic Plane at 10-15 GHz, capable of resolving physical scales smaller than 0.05 pc at distances up to 20 kpc. This is precisely the goal of the SKA-Mid Galactic Plane survey, which will, with its unprecedented sensitivity, angular resolution, and mapping speed, provide the first panoptic view of ionised gas and stellar feedback across the Milky Way.

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A global view on star formation: The GLOSTAR Galactic plane survey XII. Effelsberg's continuum view and data release

Extended radio continuum emission and its linear polarization play a key role in probing large-scale structures of synchrotron and free-free emission in the Milky Way. Despite the existence of many radio continuum surveys, sensitive and high-angular-resolution single-dish surveys of extended radio continuum emission remain scarce. As part of the GLObal view of STAR formation (GLOSTAR) survey, we will also crucially complement the existing data from the Karl G. Jansky Very Large Array (VLA) by addressing the missing zero-spacing gap. Within the framework of the GLOSTAR Galactic plane survey, we performed large-scale radio continuum imaging observations toward the Galactic plane in the range $-2^{\circ}< \ell <60^{\circ}$ and $|b|<1.1^{\circ}$, as well as the Cygnus X region with the Effelsberg 100-m radio telescope. We present the Effelsberg continuum survey at 4.89GHz and 6.82GHz including linear polarization with angular resolutions of 145$^{\prime\prime}$ and 106$^{\prime\prime}$, respectively. The survey has been corrected for missing large-scale emission using available low-angular-resolution surveys. Comparison with previous single-dish surveys indicates that our continuum survey represents the highest-quality single-dish data collected to date at this frequency. More than 90\% of the flux density missed by the VLA D-array data is effectively recovered by the Effelsberg continuum survey. The improved sensitivity and angular resolution of our survey enable reliable mapping of Galactic magnetic field structures, with polarization data that are less affected by depolarization than in previous surveys. The GLOSTAR single-dish continuum data will be released publicly, offering a valuable resource for studying extended objects including HII regions, supernova remnants, diffuse interstellar medium, and Galactic structure. (Abridged)

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A compact Keplerian-like disc and H30$α$ emission towards the radio jet in the massive protostar W75N(B)-VLA3

Studying young, high-mass stellar objects is challenging for testing models of massive star formation due to their great distances, often kiloparsecs away. This requires extremely high-angular resolution to resolve features like accretion discs around massive protostars. Consequently, while powerful, collimated outflows are evident in massive protostars, the compact accretion discs anticipated at their centres are still proving difficult to pinpoint. This study presents ALMA continuum and molecular line observations at 1.3 mm of the massive protostar W75N(B)-VLA3. The observations achieve an angular resolution of $\sim$0.12$^{\prime\prime}$ ($\sim$156 au). Dense gas tracers reveal a circumstellar disc of $\sim$450 au in radius surrounding VLA3, with an orientation perpendicular to its associated thermal radio jet. From the millimetre continuum, a total mass of $\approx$0.43-1.74 $M_\odot$ is estimated for the disc. The disc's velocity profile is consistent with Keplerian rotation around a protostar of $\approx$16 $M_\odot$. This adds VLA3 to the small number of massive disc-protostar-jet systems documented in the literature with a centrifugally supported disc with a radius less than 500 au. Additionally, we detected H30$α$ recombination line emission towards the radio jet powered by VLA3. Despite limitations in the spatial and spectral resolution, our data reveal a very broad line, indicative of high-velocity motions, as well as a tentative velocity gradient in the jet's direction, thus favouring the H30$α$ emission to originate from the radio jet. Should this interpretation be confirmed with new observations, W75N(B)-VLA3 could represent the first protostellar radio jet for which a thermal radio recombination line has been detected.

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A global view on star formation: The GLOSTAR Galactic plane survey. IX. Radio Source Catalog III: 2<l<28, 36<l<40, 56<l<60 and |b|<1, VLA B-configuration

As part of the GLOSTAR (GLObal view of STAR formation in the Milky Way) survey, we present the high-resolution continuum source catalog for the regions (l = 2-28, 36-40, 56-60, &|b|<1.0), observed with the Karl G. Jansky Very Large Array (VLA) in its B-configuration. The continuum images are optimized to detect compact sources on angular scales up to 4", and have a typical noise level of 1sigma ~ 0.08mJy/beam for an angular resolution of 1", which makes GLOSTAR currently the highest resolution as well as the most sensitive radio survey of the northern Galactic plane at 4-8GHz. We extracted 13354 sources above a threshold of 5sigma and 5437 sources above 7sigma that represent the high-reliability catalog. We determined the in-band spectral index (alpha) for the sources in the 7sigma-threshold catalog. The mean value is alpha=-0.6, which indicates that the catalog is dominated by sources emitting non-thermal radio emission. We identified the most common source types detected in radio surveys: 251 HII region candidates (113 new), 282 planetary nebulae (PNe) candidates (127 new), 784 radio star candidates (581 new), and 4080 extragalactic radio source candidates (2175 new). A significant fraction of HII regions and PNe candidates have alpha<-0.1 indicating that these candidates could contain radio jets, winds or outflows from high-mass and low-mass stellar objects. We identified 245 variable radio sources by comparing the flux densities of compact sources from the GLOSTAR survey and the Co-Ordinated Radio `N' Infrared Survey for High-mass star formation (CORNISH), and find that most of them are infrared quiet. The catalog is typically 95% complete for point sources at a flux density of 0.6 mJy (i.e. typical 7sigma level) and the systematic positional uncertainty is <= 0.1". The GLOSTAR data and catalogs are available online at https://glostar.mpifr-bonn.mpg.de.

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Modest dust settling in the IRAS04302+2247 Class I protoplanetary disk

We present new VLA observations, between 6.8mm and 66mm, of the edge-on Class~I disk IRAS04302+2247. Observations at 6.8mm and 9.2mm lead to the detection of thermal emission from the disk, while shallow observations at the other wavelengths are used to correct for emission from other processes. The disk radial brightness profile transitions from broadly extended in previous ALMA 0.9mm and 2.1mm observations to much more centrally brightened at 6.8mm and 9.2mm, which can be explained by optical depth effects. The radiative transfer modeling of the 0.9mm, 2.1mm, and 9.2mm data suggests that the grains are smaller than 1cm in the outer regions of the disk and allows us to obtain the first lower limit for the scale height of grains emitting at millimeter wavelengths in a protoplanetary disk. We find that the millimeter dust scale height is between 1au and 6au at a radius 100au from the central star, while the gas scale height is estimated to be about 7au, indicating a modest level of settling. The estimated dust height is intermediate between less evolved Class 0 sources, that are found to be vertically thick, and more evolved Class II sources, which show a significant level of settling. This suggests that we are witnessing an intermediate stage of dust settling.

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A global view on star formation: The GLOSTAR Galactic plane survey. VI. Radio Source Catalog II: $28^\circ < \ell < 36^\circ$ and $|b| < 1^\circ$, VLA B-configuration

As part of the GLOSTAR survey we have used the VLA in its B-configuration to observe the part of the Galactic plane between longitudes of 28d and 36d and latitudes from -1d to +1d at the C-band (4--8 GHz). To reduce the contamination of extended sources that are not well recovered by our coverage of the (u, v)-plane we discarded short baselines that are sensitive to emission on angular scales $<4"$. The resulting radio continuum images have an angular resolution of 1.0", and sensitivity of $\sim60 μ$Jy~beam$^{-1}$; making it the most sensitive radio survey covering a large area of the Galactic plane with this angular resolution. An automatic source extraction algorithm was used in combination with visual inspection to identify a total of 3325 radio sources. A total of 1457 radio sources are $\geq7σ$ and comprise our highly reliable catalog; 72 of these are grouped as 22 fragmented sources, e.g., multiple components of an extended and resolved source. To explore the nature of the catalogued radio sources we searched for counterparts at millimeter and infrared wavelengths. Our classification attempts resulted in 93 HII region candidates, 104 radio stars, 64 planetary nebulae, while most of the remaining radio sources are suggested to be extragalactic sources. We investigated the spectral indices ($α$, $S_ν\proptoν^α$) of radio sources classified as HII region candidates and found that many have negative values. This may imply that these radio sources represent young stellar objects that are members of the star clusters around the high mass stars that excite the HII regions, but not these HII regions themselves. By comparing the peak flux densities from the GLOSTAR and CORNISH surveys we have identified 49 variable radio sources, most of them with an unknown nature. Additionally, we provide the list of 1866 radio sources detected within 5 to 7$σ$ levels.

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Modeling the accretion disk around the high-mass protostar GGD 27-MM1

Recent high-angular resolution (40 mas) ALMA observations at 1.14 mm resolve a compact (R~200 au) flattened dust structure perpendicular to the HH 80-81 jet emanating from the GGD 27-MM1 high-mass protostar, making it a robust candidate for a true accretion disk. The jet/disk system (HH 80-81 / GGD 27-MM1) resemble those found in association with low- and intermediate-mass protostars. We present radiative transfer models that fit the 1.14 mm ALMA dust image of this disk which allow us to obtain its physical parameters and predict its density and temperature structure. Our results indicate that this accretion disk is compact (Rdisk~170 au) and massive (5Msun), about 20% of the stellar mass of 20 Msun. We estimate the total dynamical mass of the star-disk system from the molecular line emission finding a range between 21 and 30 Msun, which is consistent with our model. We fit the density and temperature structures found by our model with power law functions. These results suggest that accretion disks around massive stars are more massive and hotter than their low-mass siblings, but they still are quite stable. We also compare the temperature distribution in the GGD 27-MM1 disk with that found in low- and intermediate-mass stars and discuss possible implications on the water snow line. We have also carried about a study of the distance based on Gaia DR2 data and the population of young stellar objects (YSOs) in this region, and from the extinction maps. We conclude that the source distance is in within 1.2 and 1.4 kpc, closer than what was derived in previous studies (1.7 kpc).

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GLOSTAR -- Radio Source Catalog I: $28^{\circ}< \textit{l} < 36^{\circ}$ and $|b| < 1^{\circ}$

The GLOSTAR survey will study the star formation in the Galactic plane between $-2^{\circ}< \textit{l}< 85^{\circ}$ and $|b| < 1^{\circ}$ with unprecedented sensitivity in both, flux density ($\sim$ 40 $μJy$ beam$^{-1}$) and range of angular scales ($\sim$ 1."5 to the largest radio structures in the Galaxy). In this paper we present the first results obtained from a radio continuum map of a 16 square degree sized region of the Galactic plane centered on $\textit{l} = 32^{\circ}$ and $b = 0^{\circ}$ ($28^{\circ} < \textit{l} < 36^{\circ}$ and $|b| < 1^{\circ}$). This map has a resolution of 18" and sensitivity of $\sim$ 60-150 $μJy$ beam$^{-1}$. We present data acquired with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and centred at 4.7 and 6.9 GHz. These data were calibrated and imaged using the $\textit{Obit}$ software package. The source extraction has been performed using the BLOBCAT software package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By cross-matching with other catalogs and calculating the spectral indices ($S(ν) \propto ν^α$), we have classified 231 continuum sources as HII regions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature and relation with previously reported. These first GLOSTAR results have increased the number of reliable HII regions in this part of the Galaxy by a factor of four.

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Protostellar Outflows at the EarliesT Stages (POETS). II. A possible radio synchrotron jet associated with the EGO G035.02+0.35

Centimeter continuum observations of protostellar jets have revealed the presence of knots of shocked gas where the flux density decreases with frequency. This spectrum is characteristic of nonthermal synchrotron radiation and implies the presence of both magnetic fields and relativistic electrons in protostellar jets. Here, we report on one of the few detections of nonthermal jet driven by a young massive star in the star-forming region G035.02$+$0.35. We made use of the NSF's Karl G. Jansky Very Large Array (VLA) to observe this region at C, Ku, and K bands with the A- and B-array configurations, and obtained sensitive radio continuum maps down to a rms of 10 $μ$Jy beam$^{-1}$. These observations allow for a detailed spectral index analysis of the radio continuum emission in the region, which we interpret as a protostellar jet with a number of knots aligned with extended 4.5 $μ$m emission. Two knots clearly emit nonthermal radiation and are found at similar distances, of approximately 10,000 au, each side of the central young star, from which they expand at velocities of hundreds km s$^{-1}$. We estimate both the mechanical force and the magnetic field associated with the radio jet, and infer a lower limit of $0.4\times10^{-4} $M$_{\odot}$ yr$^{-1}$ km s$^{-1}$ and values in the range $0.7-1.3 $mG, respectively.

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Discovery of a sub-Keplerian disk with jet around a 20Msun young star. ALMA observations of G023.01-00.41

It is well established that Solar-mass stars gain mass via disk accretion, until the mass reservoir of the disk is exhausted and dispersed, or condenses into planetesimals. Accretion disks are intimately coupled with mass ejection via polar cavities, in the form of jets and less collimated winds, which allow mass accretion through the disk by removing a substantial fraction of its angular momentum. Whether disk accretion is the mechanism leading to the formation of stars with much higher masses is still unclear. Here, we are able to build a comprehensive picture for the formation of an O-type star, by directly imaging a molecular disk which rotates and undergoes infall around the central star, and drives a molecular jet which arises from the inner disk regions. The accretion disk is truncated between 2000-3000au, it has a mass of about a tenth of the central star mass, and is infalling towards the central star at a high rate (6x10^-4 Msun/yr), as to build up a very massive object. These findings, obtained with the Atacama Large Millimeter/submillimeter Array at 700au resolution, provide observational proof that young massive stars can form via disk accretion much like Solar-mass stars.

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Resolving the polarized dust emission of the disk around the massive star powering the HH~80-81 radio jet

Here we present deep (16 mumJy), very high (40 mas) angular resolution 1.14 mm, polarimetric, Atacama Large Millimeter/submillimeter Array (ALMA) observations towards the massive protostar driving the HH 80-81 radio jet. The observations clearly resolve the disk oriented perpendicular to the radio jet, with a radius of ~0.171 arcsec (~291 au at 1.7 kpc distance). The continuum brightness temperature, the intensity profile, and the polarization properties clearly indicate that the disk is optically thick for a radius of R<170 au. The linear polarization of the dust emission is detected almost all along the disk and its properties suggest that dust polarization is produced mainly by self-scattering. However, the polarization pattern presents a clear differentiation between the inner (optically thick) part of the disk and the outer (optically thin) region of the disk, with a sharp transition that occurs at a radius of 0.1 arcsec (~170 au). The polarization characteristics of the inner disk suggest that dust settling has not occurred yet with a maximum dust grain size between 50 and 500 mum. The outer part of the disk has a clear azimuthal pattern but with a significantly higher polarization fraction compared to the inner disk. This pattern is broadly consistent with self-scattering of a radiation field that is beamed radially outward, as expected in the optically thin outer region, although contribution from non-spherical grains aligned with respect to the radiative flux cannot be excluded.

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A comparison of the radio and optical time-evolution of HH~1 and 2

We present a comparison between the time-evolution over the past $\sim 20$ years of the radio continuum and H$α$ emission of HH~1 and 2. We find that the radio continuum and the H$α$ emission of both objects show very similar trends, with HH~1 becoming fainter and HH~2 brightening quite considerably (about a factor of 2). We also find that the $F_{\rm Hα}/F_{ff}$ (H$α$ to free-free continuum) ratio of HH~1 and 2 has higher values than the ones typically found in planetary nebulae (PNe) which we interpret as an indication that the H$α$ and free-free emission of HH~1/2 is produced in emitting regions with lower temperatures ($\sim 2000$~K) than the emission of PNe (with $\sim 10^4$~K).

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The Radio Jet Associated with the Multiple V380 Ori System

The giant Herbig-Haro object 222 extends over $\sim$6$'$ in the plane of the sky, with a bow shock morphology. The identification of its exciting source has remained uncertain over the years. A non-thermal radio source located at the core of the shock structure was proposed to be the exciting source. However, Very Large Array studies showed that the radio source has a clear morphology of radio galaxy and a lack of flux variations or proper motions, favoring an extragalactic origin. Recently, an optical-IR study proposed that this giant HH object is driven by the multiple stellar system V380 Ori, located about 23$'$ to the SE of HH 222. The exciting sources of HH systems are usually detected as weak free-free emitters at centimeter wavelengths. Here we report the detection of an elongated radio source associated with the Herbig Be star or with its close infrared companion in the multiple V380 Ori system. This radio source has the characteristics of a thermal radio jet and is aligned with the direction of the giant outflow defined by HH~222 and its suggested counterpart to the SE, HH~1041. We propose that this radio jet traces the origin of the large scale HH outflow. Assuming that the jet arises from the Herbig Be star, the radio luminosity is a few times smaller than the value expected from the radio-bolometric correlation for radio jets, confirming that this is a more evolved object than those used to establish the correlation.

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The Spanish Square Kilometre Array White Book

The Square Kilometre Array (SKA) is called to revolutionise essentially all areas of Astrophysics. With a collecting area of about a square kilometre, the SKA will be a transformational instrument, and its scientific potential will go beyond the interests of astronomers. Its technological challenges and huge cost requires a multinational effort, and Europe has recognised this by putting the SKA on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI). The Spanish SKA White Book is the result of the coordinated effort of 120 astronomers from 40 different research centers. The book shows the enormous scientific interest of the Spanish astronomical community in the SKA and warrants an optimum scientific exploitation of the SKA by Spanish researchers, if Spain enters the SKA project.

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The Peculiar Radio Source M17 JVLA 35

M17 JVLA 35 is a radio source detected in projection against the M17 HII region. In recent observations, its spectrum between 4.96 and 8.46 GHz was found to be positive and very steep, with $α\geq 2.9 \pm 0.6$ ($S_ν\propto ν^α$). Here we present Very Large Array observations made in the 18.5 to 36.5 GHz region that indicate a spectral turnover at $\sim$13 GHz and a negative spectral index ($α\simeq -2.0$) at higher frequencies. The spectrum is consistent with that of an extragalactic High Frequency Peaker (HFP). However, M17 JVLA 35 has an angular size of $\sim0\rlap.{''}5$ at 8.46 GHz, while HFPs have extremely compact, milliarcsecond dimensions. We discuss other possible models for the spectrum of the source and do not find them feasible. Finally, we propose that M17 JVLA35 is indeed an HFP but that its angular size becomes broadened by plasma scattering as its radiation travels across M17. If our interpretation is correct, accurate measurements of the angular size of M17 JVLA35 across the centimeter range should reveal the expected $ν^{-2}$ dependence.

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Signatures of infall motions in the images of the molecular emission of G31 HMC

Although gravitational collapse is supposed to play an essential role in the star formation process, infall motions have been always elusive to detect. So far, only a few observational signatures have been commonly used to claim for the presence of infall. Often these features consist in either "blue-asymmetries" or absorption at red-shifted velocities (e.g., inverse P-Cygni profiles). Both signatures are based only on the shape of the line profile and they do not guarantee by themselves the presence of dominant infall motions. More robust "mapping signatures" can be obtained from images that angularly resolve the infalling gas. Here we present VLA observations of the ammonia inversion transitions (2,2), (3,3), (4,4), (5,5), and (6,6) towards the hot molecular core (HMC) near G31.41+0.31 that show the signatures of protostellar infall theoretically predicted by Anglada et al. (1991). The intensity of the ammonia emission is compact and sharply increases towards the centre in the blue-shifted velocity channel maps, while it shows a more flattened distribution in the red-shifted velocity channels. Additionally, the emission becomes more compact with increasing (relative) velocity for both red and blue-shifted channels. We introduce a new infall signature, the "central blue spot", easily identifiable in the first-order moment maps. We show that rotation produces an additional, independent signature, making the distribution of the emission in the channel maps asymmetric with respect to the central position, but without masking the infall signatures. All these mapping signatures, which are identified here for the first time, are present in the observed ammonia transitions of G31 HMC.

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Multiplicity, Disks and Jets in the NGC 2071 Star-Forming Region

We present centimeter and millimeter observations of the NGC 2071 star-forming region performed with the VLA and CARMA. We detected counterparts at 3.6 cm and 3 mm for the previously known sources IRS 1, IRS 2, IRS 3, and VLA 1. All these sources show SEDs dominated by free-free thermal emission at cm wavelengths, and thermal dust emission at mm wavelengths, suggesting that all of them are associated with YSOs. IRS 1 shows a complex morphology at 3.6 cm, with changes in the direction of its elongation. We discuss two possible explanations to this morphology: the result of changes in the direction of a jet due to interactions with a dense ambient medium, or that we are actually observing the superposition of two jets arising from two components of a binary system. Higher angular resolution observations at 1.3 cm support the second possibility, since a double source is inferred at this wavelength. IRS 3 shows a clear jet-like morphology at 3.6 cm. Over a time-span of four years, we observed changes in the morphology of this source that we interpret as due to ejection of ionized material in a jet. The emission at 3 mm of IRS 3 is angularly resolved, with a deconvolved size (FWHM) of ~120 AU, and seems to be tracing a dusty circumstellar disk perpendicular to the radio jet. An irradiated accretion disk model around an intermediate-mass YSO can account for the observed SED and spatial intensity profile at 3 mm, supporting this interpretation.

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HH 223: a parsec-scale H2 outflow in the star-forming region L723

The dark cloud Lynds 723 (L723) is a low-mass star-forming region where one of the few known cases of a quadrupolar CO outflow has been reported. Two recent works have found that the radio continuum source VLA 2, towards the centre of the CO outflow, is actually a multiple system of young stellar objects (YSOs). Several line-emission nebulae that lie projected on the east-west CO outflow were detected in narrow-band Halpha and [SII] images. The spectra of the knots are characteristic of shock-excited gas (Herbig-Haro spectra), with supersonic blueshifted velocities, which suggests an optical outflow also powered by the VLA 2 YSO system of L723. We imaged a field of ~5' X 5' centred on HH 223, which includes the whole region of the quadrupolar CO outflow with nir narrow-band filters . The H2 line-emission structures appear distributed over a region of 5.5' (0.5 pc for a distance of 300 pc) at both sides of the VLA 2 YSO system, with an S-shape morphology, and are projected onto the east-west CO outflow. Most of them were resolved in smaller knotty substructures. The [FeII] emission only appears associated with HH 223. An additional nebular emission from the continuum in Hc and Kc appears associated with HH 223-K1, the structure closest to the VLA 2 YSO system, and could be tracing the cavity walls. We propose that the H2 structures form part of a large-scale near-infrared outflow, which is also associated with the VLA 2 YSO system. The current data do not allow us to discern which of the YSOs of VLA 2 is powering this large scale optical/near-infrared outflow.

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