Young Star Clusters Research Articles

The Effect of Metallicity on the Formation of Massive Black Holes through Stellar Collisions in Young Massive Star Clusters

Dynamical interactions facilitated by the high densities in massive star clusters can lead to large numbers of stellar collisions and unique stellar evolution pathways not possible for stars evolving in isolation. Using N-body cluster models, we study the role of stellar collisions in the formation of massive black holes, specifically studying the effect of stellar metallicity on this process. We show that at high metallicity (up to solar), the number of massive black holes formed may be reduced by up to a factor of ten compared to low-metallicity clusters. We also examine the role of collisions in the production of pair-instability supernovae and predict event rates of these transients in the local universe.

Detection of Diffuse γ-Ray Emission toward a Massive Star-forming Region Hosting Wolf–Rayet Stars

Isotopic and elemental abundances seen in Galactic cosmic rays (GCRs) imply that ∼20% of the cosmic-ray (CR) nuclei are probably synthesized by massive Wolf–Rayet (W-R) stars. Massive star clusters hosting W-R- and OB-type stars have been proposed as potential GCR accelerators for decades, in particular via diffusive shock acceleration at wind termination shocks. Here we report the analysis of Fermi Large Area Telescope data toward the direction of Masgomas-6a, a young massive star cluster candidate hosting two W-R stars. We detect an extended γ-ray source with a test statistic = 183 in the vicinity of Masgomas-6a, spatially coincident with two unassociated Fermi 4FGL sources. We also present the CO observational results of molecular clouds in this region, using the data from the Milky Way Imaging Scroll Painting project. The γ-ray emission intensity correlates well with the distribution of molecular gas at the distance of Masgomas-6a, indicating that these γ-rays may be produced by CRs accelerated by massive stars in Masgomas-6a. At the distance of 3.9 kpc of Masgomas-6a, the luminosity of the extended source is (1.81 ± 0.02) × 1035 erg s−1. With a kinetic luminosity of ∼1037 erg s−1 in the stellar winds, the W-R stars are capable of powering the γ-ray emission via neutral pion decay resulted from CR proton–proton interactions. The size of the GeV source and the energetic requirement suggests a CR diffusion coefficient smaller than that in the Galactic interstellar medium, indicating a strong suppression of CR diffusion in the molecular cloud.

Galactic Winds and Bubbles from Nuclear Starburst Rings

Galactic outflows from local starburst galaxies typically exhibit a layered geometry, with cool 104 K flow sheathing a hotter 107 K, cylindrically collimated, X-ray-emitting plasma. Here we argue that winds driven by energy injection in a ring-like geometry can produce this distinctive large-scale multiphase morphology. The ring configuration is motivated by the observation that massive young star clusters are often distributed in a ring at the host galaxy’s inner Lindblad resonance, where larger-scale spiral arm structure terminates. We present parameterized three-dimensional radiative hydrodynamical simulations that follow the emergence and dynamics of energy-driven hot winds from starburst rings. In this letter, we show that the flow shocks on itself within the inner ring hole, maintaining high 107 K temperatures, while flows that emerge from the wind-driving ring unobstructed can undergo rapid bulk cooling down to 104 K, producing a fast hot biconical outflow enclosed by a sheath of cooler nearly comoving material without ram pressure acceleration. The hot flow is collimated along the ring axis, even in the absence of pressure confinement from a galactic disk or magnetic fields. In the early stages of expansion, the emerging wind forms a bubble-like shape reminiscent of the Milky Way’s eROSITA and Fermi bubbles and can reach velocities usually associated with active-galactic-nucleus-driven winds. We discuss the physics of the ring configuration, the conditions for radiative bulk cooling, and the implications for future X-ray observations.

Can superbubbles accelerate ultrahigh energy protons?

ABSTRACT We critically assess limits on the maximum energy of protons accelerated within superbubbles around massive stellar clusters, considering a number of different scenarios. In particular, we derive under which circumstances acceleration of protons above peta-electronvolt (PeV) energies can be expected. While the external forward shock of the superbubble may account for acceleration of particles up to 100 TeV, internal primary shocks such as supernova remnants expanding in the low density medium or the collective wind termination shock which forms around a young compact cluster provide more favourable channels to accelerate protons up to 1 PeV, and possibly beyond. Under reasonable conditions, clustered supernovae launching powerful shocks into the magnetized wind of a young and compact massive star cluster are found to be the most promising systems to accelerate protons above 10 PeV. On the other hand, stochastic re-acceleration in the strongly turbulent plasma is found to be much less effective than claimed in previous works, with a maximum proton energy of at most a few hundred TeV.

NGC1818 unveils the origin of the extended main-sequence turn-off in young Magellanic Clouds clusters

The origin of young star clusters represents a major challenge for modern stellar astrophysics. While stellar rotation partially explains the colour spread observed along main-sequence turn-offs, i.e. where stars leave the main-sequence after the exhaustion of hydrogen in their core, and the multiple main sequences in the colour-magnitude diagrams of stellar systems younger than approximately 2 Gyr, it appears that an age difference may still be required to fulfill the observational constraints. Here we introduce an alternative approach that exploits the main-sequence turn-on, i.e. the point alongside the colour-magnitude diagram where pre-main-sequence stars join the main-sequence, to disentangle between the effects of stellar rotation and age to assess the presence, or lack thereof, of prolonged star formation in the approximately 40-Myr-old cluster NGC1818. Our results provide evidence for a fast star formation, confined within 8 Myr, thus excluding age differences as responsible for the extended main-sequence turn-offs, and leading the way to alternative observational perspectives in the exploration of stellar populations in young clusters.

Quantifying kinematic substructure in star-forming regions with statistical tests of spatial autocorrelation

ABSTRACT We investigate whether spatial-kinematic substructure in young star-forming regions can be quantified using Moran’s I statistic. Its presence in young star clusters would provide an indication that the system formed from initially substructured conditions, as expected by the hierarchical model of star cluster formation, even if the cluster were spatially smooth and centrally concentrated. Its absence, on the other hand, would be evidence that star clusters form monolithically. The Moran’s I statistic is applied to N-body simulations of star clusters with different primordial spatial-velocity structures, and its evolution over time is studied. It is found that this statistic can be used to reliably quantify spatial-kinematic substructure, and can be used to provide evidence as to whether the spatial-kinematic structure of regions with ages ≲6 Myr is best reproduced by the hierarchical or monolithic models of star formation. Moran’s I statistic is also able to conclusively say whether the data are not consistent with initial conditions that lack kinematic substructure, such as the monolithic model, in regions with ages up to, and potentially beyond, 10 Myrs. This can therefore provide a kinematic signature of the star cluster formation process that is observable for many Myr after any initial spatial structure has been erased.

The origin of close massive binaries in the M17 star-forming region

Context.Spectroscopic multiplicity surveys of O stars in young clusters and OB associations have revealed that a large portion (∼70%) of these massive stars (Mi > 15M⊙) belong to close and short-period binaries (with a physical separation of less than a few astronomical units). Follow-up VLT(I) high-angular-resolution observations led to the detection of wider companions (up tod ∼ 500 au), increasing the average companion fraction to > 2. Despite the recent and significant progress, the formation mechanisms leading to such close massive multiple systems remain to be elucidated. As a result, young massive close binaries (or higher-order multiple systems) are unique laboratories for determining the pairing mechanism of high-mass stars.Aims.We present the first VLTI/GRAVITY observations of six young O stars in the M17 star-forming region (≲1 Myr) and two additional foreground stars. VLTI/GRAVITY provides theK-band high-angular-resolution observations needed to explore the close environment of young O-type stars, and, as such, offers an excellent opportunity to characterise the multiplicity properties of the immediate outcome of the massive star formation process.Methods.From the interferometric model fitting of visibility amplitudes and closure phases, we search for companions and measure their positions and flux ratios. Combining the resulting magnitude difference with atmosphere models and evolutionary tracks, we further constrain the masses of the individual components.Results.All six high-mass stars are in multiple systems, leading to a multiplicity fraction of 100% and yielding a 68% confidence interval of 94–100%. We detect a total of nine companions with separations of up to 120 au. Including previously identified spectroscopic companions, the companion fraction of the young O stars in our sample reaches 2.3 ± 0.6. The derived masses span a wide range, from 2.5 to 50M⊙, with a great tendency towards high-mass companions. However, we do not find a significant correlation between the mass of the companions and their separation.Conclusions.While based on a modest sample, our results clearly indicate that the origin of the high degree of multiplicity is rooted in the star formation mechanism of the sample stars. No clear evidence for one of the competing concepts of massive star formation (core accretion or competitive accretion) could be found. However, given that we find all of the companions within ∼120 au, our results are compatible with migration as a scenario for the formation of close massive binaries.

Dust Grain Growth and Dusty Supernovae in Low-metallicity Molecular Clouds

We present 3D hydrodynamical models of the evolution of superbubbles powered by stellar winds and supernovae from young coeval massive star clusters within low-metallicity (Z = 0.02 Z ⊙), clumpy molecular clouds. We explore the initial stages of the superbubble evolution, including the occurrence of pair-instability and core-collapse supernovae. Our aim is to study the occurrence of dust grain growth within orbiting dusty clumps, and in the superbubble’s swept-up supershell. We also aim to address the survival of dust grains produced by sequential supernovae. The model accounts for the star cluster gravitational potential and self-gravity of the parent cloud. It also considers radiative cooling (including that induced by dust) and a state-of-the-art population synthesis model for the coeval cluster. As shown before, a superbubble embedded into a clumpy medium becomes highly distorted, expanding mostly due to the hot gas streaming through low-density channels. Our results indicate that in the case of massive (∼107 M ⊙) molecular clouds, hosting a super star cluster (∼5.6 × 105 M ⊙), grain growth increments the dust mass at a rate ∼4.8 × 10−5 M ⊙ yr−1 during the first 2.5 Myr of the superbubble’s evolution, while the net contribution of pair-instability and core-collapse supernovae to the superbubble’s dust budget is ∼1200 M ⊙ (M SC/5.6 × 105 M ⊙), where M SC is the stellar mass of the starburst. Therefore, dust grain growth and dust injection by supernovae lead to the creation of, without invoking a top-heavy initial mass function, massive amounts of dust within low-metallicity star-forming molecular clouds, in accordance with the large dust mass present in galaxies soon after the onset of cosmic reionization.

SN 2009ip after a decade: the luminous blue variable progenitor is now gone

ABSTRACT We present new Hubble Space Telescope (HST) imaging photometry for the site of the Type IIn supernova (SN) 2009ip taken almost a decade after explosion. The optical source has continued to fade steadily since the SN-like event in 2012. In the F606W filter, which was also used to detect its luminous blue variable (LBV) progenitor 13 yr before the SN, the source at the position of SN 2009ip is now 1.2 mag fainter than that quiescent progenitor. It is 6–7 mag fainter than the pre-SN outbursts in 2009–2011. This definitively rules out a prediction that the source would return to its previous state after surviving the 2012 event. Instead, the late-time fading matches expectations for a terminal explosion. The source fades at a similar rate in all visual-wavelength filters without significant colour changes, therefore also ruling out the hypothesis of a luminous dust-obscured survivor or transition to a hotter post-LBV survivor. The late-time continuum with steady colour and strong Hα emission detected in a narrow F657N filter are, however, entirely expected for ongoing shock interaction with circumstellar material in a decade-old core-collapse SN. Interestingly, the ultraviolet flux has stayed nearly constant since 2015, supporting previous conjectures that the F275W light traces main-sequence OB stars in an underlying young star cluster. We expect that the visual-wavelength continuum will eventually level off, tracing this cluster light. Without any additional outbursts, it seems prudent to consider the 2012 event as a terminal SN explosion, and we discuss plausible scenarios.

The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – III. The Large Magellanic Cloud

ABSTRACT We present a map of the total intrinsic reddening across ≃ 90 deg2 of the Large Magellanic Cloud (LMC) derived using optical (ugriz) and near-infrared (IR; YJKs) spectral energy distributions (SEDs) of background galaxies. The reddening map is created from a sample of 222 752 early-type galaxies based on the lephareχ2 minimization SED-fitting routine. We find excellent agreement between the regions of enhanced intrinsic reddening across the central (4 × 4 deg2) region of the LMC and the morphology of the low-level pervasive dust emission as traced by far-IR emission. In addition, we are able to distinguish smaller, isolated enhancements that are coincident with known star-forming regions and the clustering of young stars observed in morphology maps. The level of reddening associated with the molecular ridge south of 30 Doradus is, however, smaller than in the literature reddening maps. The reduced number of galaxies detected in this region, due to high extinction and crowding, may bias our results towards lower reddening values. Our map is consistent with maps derived from red clump stars and from the analysis of the star formation history across the LMC. This study represents one of the first large-scale categorizations of extragalactic sources behind the LMC and as such we provide the lephare outputs for our full sample of ∼ 2.5 million sources.

SIRIUS Project – V. Formation of off-centre ionized bubbles associated with Orion Nebula Cluster

ABSTRACT Massive stars born in star clusters terminate star cluster formation by ionizing the surrounding gas. This process is considered to be prevalent in young star clusters containing massive stars. The Orion Nebula is an excellent example associated with a forming star cluster including several massive stars (the Orion Nebula Cluster, ONC) and a 2-pc-sized H ii region (ionized bubble) opening towards the observer; however, the other side is still covered with dense molecular gas. Recent astrometric data acquired by the Gaia satellite revealed the stellar kinematics in this region. By comparing these data with star cluster formation simulation results, we demonstrate that massive stars born in the ONC centre were ejected via three-body encounters. Further, orbit analysis indicates that θ2 Ori A, the second massive star in this region, was ejected from the ONC centre towards the observer and is now returning to the cluster centre. Such ejected massive stars can form a hole in the dense molecular cloud and contribute to the formation of the 2-pc bubble. Our results demonstrate that the dynamics of massive stars are essential for the formation of star clusters and H ii regions that are not always centred by massive stars.

When Do Stars Go Boom?

The maximum mass of a star that can produce a white dwarf (WD) is an important astrophysical quantity. One of the best approaches to establishing this limit is to search for WDs in young star clusters in which only massive stars have had time to evolve and where the mass of the progenitor can be established from the cooling time of the WD together with the age of the cluster. Searches in young Milky Way clusters have not thus far yielded WD members more massive than about 1.1 M ⊙, well below the Chandrasekhar mass of 1.38 M ⊙, nor progenitors with masses in excess of about 6 M ⊙. However, the hunt for potentially massive WDs that escaped their cluster environs is yielding interesting candidates. To expand the cluster sample further, we used HST to survey four young and massive star clusters in the Magellanic Clouds for bright WDs that could have evolved from stars as massive as 10 M ⊙. We located five potential WD candidates in the oldest of the four clusters examined, the first extragalactic single WDs thus far discovered. As these hot WDs are very faint at optical wavelengths, final confirmation will likely have to await spectroscopy with 30 m class telescopes.

Gamma-ray observation towards the young massive star cluster NGC 6618 in the M17 region

ABSTRACT Young massive clusters have been established as a new population of gamma-ray sources and potential cosmic ray (CR) accelerators. In this paper, we report the detection of gamma-ray emissions near the young star cluster NGC 6618, which is one of the youngest star clusters in our Galaxy. The detected gamma-ray emissions can be divided into two components. One component is point-like and reveals harder spectrum, while the other is extended and with softer spectrum. Such spectral features are significantly different from other young massive clusters and may be due to the propagation effects of CRs accelerated in NGC 6618.

The SUNBIRD survey: the K-band luminosity functions of young massive clusters in intensely star-forming galaxies

ABSTRACT Strongly star-forming galaxies are prolific in producing the young and most massive star clusters still forming today. This work investigates the star cluster luminosity functions (CLFs, dN/dL ∝ L−α) of 26 starburst and luminous infrared galaxies taken from the SUNBIRD survey. The targets were imaged using near-infrared K-band adaptive optics systems. Single power-law fits of the derived CLFs result in a slope α ranging between 1.53 and 2.41, with the median and average of 1.87 ± 0.23 and 1.93 ± 0.23, respectively. Possible biases such as blending effects and the choice of binning should only flatten the slope by no more than ∼0.15, especially for cases where the luminosity distance of the host galaxy is below 100 Mpc. Results from this follow-up study strengthen the conclusion from our previous work: the CLF slopes are shallower for strongly star-forming galaxies in comparison to those with less intense star formation activity. There is also a (mild) correlation between α and both the host galaxy’s star formation rate (SFR) and SFR density (ΣSFR), i.e. the CLF flattens with an increasing SFR and ΣSFR. Finally, we also find that CLFs on subgalactic scales associated with the nuclear regions of cluster-rich targets (N ≈ 300) have typically shallower slopes than the ones of the outer field by ∼0.5. Our analyses suggest that the extreme environments of strongly star-forming galaxies are likely to influence the cluster formation mechanisms and ultimately their physical properties.

An Infrared View of the Obscured AGN Environment in NGC 4945

NGC 4945 harbors one of the nearest active galactic nuclei (AGNs), which allows us to reach high spatial resolution with current observational facilities. The Seyfert 2 nucleus is deeply obscured by an edge-on disk with A V ∼ 14, requiring infrared observations to study circumnuclear structures and the interstellar medium. In this work, we present an imaging and long-slit spectroscopic study of the nuclear region with a spatial resolution of 6.5 pc, based on Flamingos-2 (F2) and T-ReCS data taken at the Gemini South observatory. We report subarcsecond photometric measurements of the nucleus in J, H, and K s filters, and at larger apertures. We do not detect nuclear variability. The nuclear spectra confirm that even in the K band the AGN emission-line features are completely obscured by dust. We detect a circumnuclear disk in the K band as well as in the mid-infrared N and Q abands, with a radial scale length of ∼120 pc. The disk shows knots mostly in a ring-like arrangement that has been previously detected with Paα observations from the Hubble Space Telescope, indicating that these are deeply embedded, massive young star clusters. We present here the spectrum of one of the brightest unresolved objects (R < 5 pc), which we identify as a super star cluster candidate with . For the circumnuclear region, a detailed rotation curve allows us to measure a nuclear mass of M = (4.4 ± 3) × 106 M ⊙ within a radius of ∼6.5 pc. We also report the detection of hot dust (∼1000 K) out to a nuclear distance of 80 pc measured along the semimajor axis.

GaiaEDR3 distances of the young stellar clusters in the extended Carina Nebula complex

Context.The Carina Nebula complex (CNC) is one of the most massive and active star-forming regions in our Galaxy and it contains several large young star clusters. The distances of the individual clusters and their physical connection were poorly known up to now, with strongly discrepant results reported in the literature.Aims.We want to determine reliable distances of the young stellar clusters in the central Carina Nebula region (in particular, Tr 14, 15, and 16) and the prominent clusters NGC 3324 and NGC 3293 in the northwestern periphery of the CNC.Methods.We analyzed the parallaxes inGaiaEDR3 for a comprehensive sample of 237 spectroscopically identified OB stars, as well as for 9562 X-ray-selected young stars throughout the complex. We also performed an astrometric analysis to identify members of the young cluster vdBH 99, which is located in the foreground of the northwestern part of the Carina Nebula.Results.We find that the distances of the investigated clusters in the CNC are equal within ≤2%, and yield very consistent most likely mean distance values of 2.36−0.05+0.05kpc for the OB star sample and 2.34−0.06+0.05kpc for the sample of X-ray-selected young stars.Conclusions.Our results show that the clusters in the CNC constitute a coherent star-forming region, in particular with regard to NGC 3324 and NGC 3293 at the northwestern periphery, which are (within ≤2%) at the same distance as the central Carina Nebula. For the foreground cluster vdBH 99, we find a mean distance of 441−2+2pc and an age of ≃60 Myr. We quantified the contamination of X-ray-selected samples of Carina Nebula stars based on members of this foreground cluster.

Gaia-ESO Survey: Role of magnetic activity and starspots on pre-main-sequence lithium evolution

Context. It is now well-known that pre-main-sequence models with inflated radii should be taken into account to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern observed in young open star clusters. Aims. We tested a new set of pre-main-sequence models that include radius inflation due to the presence of starspots or to magnetic inhibition of convection. We used five clusters observed by the Gaia-ESO Survey that span the age range ∼10−100 Myr, in which these effects could be important. Methods. The Gaia-ESO Survey radial velocities were combined with astrometry from Gaia EDR3 to obtain clean lists of high-probability members for the five clusters. A Bayesian maximum likelihood method was adopted to fit the observed cluster sequences to theoretical predictions to derive the best model parameters and the cluster reddening and age. Models were calculated with different values of the mixing length parameter (αML = 2.0, 1.5 and 1.0) for the cases without spots or with effective spot coverage βspot = 0.2 and 0.4. The models were also compared with the observed lithium depletion patterns. Results. To reproduce the colour-magnitude diagram and the observed lithium depletion pattern in Gamma Vel A and B and in 25 Ori, both a reduced convection efficiency, with αML = 1.0, and an effective surface spot coverage of about 20% are required. We obtained ages of 18−4.0+1.5 Myr and 21−3.0+3.5 Myr for Gamma Vel A and B, respectively, and 19−7.0+1.5 Myr for 25 Ori. However, a single isochrone is not sufficient to account for the lithium dispersion, and an increasing level of spot coverage as mass decreases seems to be required. On the other hand, the older clusters (NGC 2451 B at 30−5.0+3.0 Myr, NGC 2547 at 35−4.0+4.0 Myr, and NGC 2516 at 138−42+48 Myr) are consistent with standard models (i.e. αML = 2.0 and no spots) except at low masses: a 20% spot coverage appears to reproduce the sequence of M-type stars better and might explain the observed spread in lithium abundances. Conclusions. The quality of Gaia-ESO data combined with Gaia allows us to gain important insights on pre-main-sequence evolution. Models including starspots can provide a consistent explanation of the cluster sequences and lithium abundances observed in young clusters, although a range of starspot coverage is required to fully reproduce the data.

Embedded Young Massive Star Clusters in the Antennae Merger

Abstract The properties of young massive clusters (YMCs) are key to understanding the star formation mechanism in starburst systems, especially mergers. We present Atacama Large Millimeter/submillimeter Array high-resolution (∼10 pc) continuum (100 and 345 GHz) data of YMCs in the overlap region of the Antennae galaxy. We identify six sources in the overlap region, including two sources that lie in the same giant molecular cloud (GMC). These YMCs correspond well with radio sources in lower-resolution continuum (100 and 220 GHz) images at GMC scales (∼60 pc). We find most of these YMCs are bound clusters through virial analysis. We estimate their ages to be ∼1 Myr and that they are either embedded or just beginning to emerge from their parent cloud. We also compare each radio source with a Paβ source, and find they have consistent total ionizing photon numbers, which indicates they are tracing the same physical source. By comparing the free–free emission at ∼10 pc scale and ∼60 pc scale, we find that ∼50% of the free–free emission in GMCs actually comes from these YMCs. This indicates that roughly half of the stars in massive GMCs are formed in bound clusters. We further explore the mass correlation between YMCs and GMCs in the Antennae and find it generally agrees with the predictions of the star cluster simulations. The most massive YMC has a stellar mass that is 1%–5% of its host GMC mass.

Diffuse GeV emission in the field of HESS J1912+101 revisited

We have analyzed 12 years of Fermi Large Area Telescope data toward the HESS J1912+101 region. With the latest source catalog and diffuse background models, a γ-ray excess is detected with a significance of ~8σ in the energy range of above 10 GeV. It has been argued that the diffuse GeV emission in the vicinity of HESS J1912+101 are from an extended pulsar wind nebula powered by PSR J1913+1011 and also that the hard GeV emission above 10 GeV stems from the shell-type supernova remnant and is connected with the TeV emissions. Different from previous works, our analysis indicates that the H2 spatial template is preferred over the other spatial templates, suggesting that the diffuse emission component spatially correlates with the dense molecular gas. This spatial correlation favors a hadronic emission scenario, although a leptonic origin cannot be ruled out. In the hadronic scenario, the parent proton spectrum can be described by a power-law function with an index of α = 2.36 ± 0.16. Above 50 GeV, there is no emission, and the upper limits reveal a spectral cutoff or break in the parent proton spectrum that can be explained as propagation effects of cosmic rays. We argue that the parent protons may come from the candidate supernova remnant HESS J1912+101 or the young massive star cluster Mc20.

Diagnosing Triggered Star Formation in the Galactic H ii region Sh 2-142

Abstract Stars are formed by gravitational collapse, spontaneously or, in some cases under the constructive influence of nearby massive stars, out of molecular cloud cores. Here we present an observational diagnosis of such triggered formation processes in the prominent H ii region Sh 2-142, which is associated with the young star cluster NGC 7380, and with some bright-rimmed clouds as the signpost of photoionization of molecular cloud surfaces. Using near- (2MASS) and mid-infrared (WISE) colors, we identified candidate young stars at different evolutionary stages, including embedded infrared sources having spectral energy distributions indicative of active accretion. We have also used data from our optical observations to be used in SEDs, and from Gaia EDR3 to study the kinematics of young objects. With this young stellar sample, together with the latest CO line emission data (spectral resolution ∼0.16 km s−1, sensitivity ∼0.5 K), a positional and aging sequence relative to the neighboring cloud complex, and to the bright-rimmed clouds, is inferred. The propagating stellar birth may be responsible, at least partially, for the formation of the cluster a few million years ago, and for the ongoing activity now witnessed in the cloud complex.