Ongoing Star Formation Research Articles

H2CO and H110α Observations toward the Aquila Molecular Cloud

Abstract The formaldehyde H2CO(110–111) absorption line and H110α radio recombination line have been observed toward the Aquila Molecular Cloud using the Nanshan 25 m telescope operated by the Xinjiang Astronomical Observatory CAS. These first observations of the H2CO (110–111) absorption line determine the extent of the molecular regions that are affected by the ongoing star formation in the Aquila molecular complex and show some of the dynamic properties. The distribution of the excitation temperature T ex for H2CO identifies the two known star formation regions W40 and Serpens South as well as a smaller new region Serpens 3. The intensity and velocity distributions of H2CO and 13CO(1−0) do not agree well with each other, which confirms that the H2CO absorption structure is mostly determined by the excitation of the molecules resulting from the star formation rather than by the availability of molecular material as represented by the distribution. Some velocity-coherent linear 13CO(1−0) structures have been identified in velocity channel maps of H2CO and it is found that the three star formation regions lie on the intersect points of filaments. The H110α emission is found only at the location of the W40 H ii region and spectral profile indicates a redshifted spherical outflow structure in the outskirts of the H ii region. Sensitive mapping of H2CO absorption of the Aquila Complex has correctly identified the locations of star formation activity in complex molecular clouds and the spectral profiles reveal the dominant velocity components and may identify the presence of outflows.

Do Galaxy Morphologies Really Affect the Efficiency of Star Formation During the Phase of Galaxy Transition?

Abstract Recent simulations predict that the presence of the stellar bulge suppress the efficiency of star formation (SF) in early-type galaxies, and this “morphological quenching” scenario is supported by many observations. In this study, we discuss the net effect of galaxy morphologies on the star formation efficiency (SFE) during the phase of galaxy transition, on the basis of our CO(J = 1 − 0) observations of 28 local “green valley” galaxies with the Nobeyama 45 m Radio Telescope. We observed 13 disk-dominated and 15 bulge-dominated green valley galaxies at fixed stellar mass (M *) and star formation rate (SFR), supplemented by 1 disk- and 6 bulge-dominated galaxies satisfying the same criteria from the xCOLD GASS survey. By using a total of 35 green valley galaxies, we reveal that the distributions of molecular gas mass, molecular gas fraction, and SFE of green valley galaxies do not change with their morphologies, suggesting little impact of galaxy morphologies on their SFE, and interestingly, this result is also valid for normal star-forming galaxies on the SF main sequence selected from the xCOLD GASS galaxies. On the other hand, we find that ∼20% of the bulge-dominated green valley galaxies do not show significant CO emission line, showing high SFEs for their M * and SFR. These molecular gas deficient sources that are identified only in the bulge-dominated green valley galaxies may represent an important population during the quenching phase under the influence of the stellar bulge, but our results suggest that the presence of the stellar bulge does not decrease the efficiency of ongoing SF, in contrast to the prediction of the morphological quenching scenario.

Variation of the Mid-infrared versus Hα Luminosity Correlation with Increasing Redshift for Galaxies in the Local Universe

Abstract The correlation between mid-infrared (MIR) and Hα luminosity (hereafter referred to as the MIR versus Hα correlation) has been investigated for years, and these approximate linear correlations have been applied to many studies to derive the ongoing star formation rate (SFR) for galaxies near and far. We present and analyze the correlations between rest-frame 12 and 22 μm and Hα luminosities for a large sample of star-forming galaxies with redshift ranging from 0.03 to 0.15 selected in the cross-matched SDSS DR7 and ALLWISE survey. For the galaxies located in a relatively narrow redshift bin (Δz ∼ 0.01), we find that the fitting slope of the MIR versus Hα correlation is always less than 1, and less than the slope derived for all the star-forming galaxies covering a broad redshift range (0.03 < z < 0.15). Additionally, the fitting intercept increases with redshift. We check the influence on the L[MIR] versus L[Hα] correlation from K- and aperture correction, the variation of either star formation history or morphology, and find their influence is not large enough to account for the inconsistency of the MIR versus Hα correlation individually. We also find that there is possible evolution for the SFR versus M* (stellar mass) correlation within the redshift coverage from 0.03 to 0.15. Finally, we warn that an unwanted error might be brought in if the MIR versus Hα correlation derived from the sample covering a large redshift interval has been applied, and indicate an explicit study is needed to establish an accurate, redshift-independent MIR versus Hα correlation.

MOSFIRE Spectroscopy of Quiescent Galaxies at 1.5 < z < 2.5. II. Star Formation Histories and Galaxy Quenching

Abstract We investigate the stellar populations for a sample of 24 quiescent galaxies at 1.5 < z < 2.5 using deep rest-frame optical spectra obtained with Keck MOSFIRE. By fitting templates simultaneously to the spectroscopic and photometric data and exploring a variety of star formation histories, we obtain robust measurements of median stellar ages and residual levels of star formation. After subtracting the stellar templates, the stacked spectrum reveals the Hα and [N ii] emission lines, providing an upper limit on the ongoing star formation rate of 0.9 ± 0.1 M ⊙ yr−1. By combining the MOSFIRE data with our sample of Keck LRIS spectra at lower redshift, we analyze the quiescent population at 1 < z < 2.5 in a consistent manner. We find a tight relation (with a scatter of 0.13 dex) between the stellar age and the rest-frame U − V and V − J colors, which can be used to estimate the age of quiescent galaxies, given their colors. Applying this age–color relation to large photometric samples, we are able to model the number density evolution for quiescent galaxies of various ages. We find evidence for two distinct quenching paths: a fast quenching that produces compact post-starburst systems and a slow quenching of larger galaxies. Fast quenching accounts for about a fifth of the growth of the red sequence at z ∼ 1.4 and half at z ∼ 2.2. We conclude that fast quenching is triggered by dramatic events, such as gas-rich mergers, while slow quenching is likely caused by a different physical mechanism.

Quasar Sightline and Galaxy Evolution (QSAGE) survey – I. The galaxy environment of O vi absorbers up to z = 1.4 around PKS 0232−04

ABSTRACT We present the first results from a study of O vi absorption around galaxies at z < 1.44 using data from a near-infrared grism spectroscopic Hubble Space Telescope Large Programme, the Quasar Sightline and Galaxy Evolution (QSAGE) survey. QSAGE is the first grism galaxy survey to focus on the circumgalactic medium at z ∼ 1, providing a blind survey of the galaxy population. The galaxy sample is H α flux limited (f(H α) > 2 × 10−17 erg s−1 cm−2) at 0.68 < z < 1.44, corresponding to ≳0.2–0.8 M⊙ yr−1. In this first of 12 fields, we combine the galaxy data with high-resolution STIS and COS spectroscopy of the background quasar to study O vi in the circumgalactic medium. At z ∼ 1, we find O vi absorption systems up to b ∼ 350 kpc (∼4Rvir) from the nearest detected galaxy. Further, we find ${\sim }50{{\ \rm per\ cent}}$ of ≳1 M⊙ yr−1 star-forming galaxies within 2Rvir show no associated O vi absorption to a limit of at least N(O vi) = 1013.9 cm−2. That we detect O vi at such large distances from galaxies and that a significant fraction of star-forming galaxies show no detectable O vi absorption disfavours outflows from ongoing star formation as the primary medium traced by these absorbers. Instead, by combining our own low- and high-redshift data with existing samples, we find tentative evidence for many strong (N(O vi) > 1014 cm−2) O vi absorption systems to be associated with M⋆ ∼ 109.5–10 M⊙ mass galaxies (Mhalo ∼ 1011.5–12 M⊙ dark matter haloes), and infer that they may be tracing predominantly collisionally ionized gas within the haloes of such galaxies.

The Next Generation Fornax Survey (NGFS). V. Discovery of a Dwarf–Dwarf Galaxy Pair at z = 0.30 and Its Characterization Using Deep VLT/MUSE Observations

We report the detection of a pair of dwarf galaxies at $z\!=\!0.30$ which may be in the early stages of an interaction. Both galaxies have stellar masses of $<10^{9}M_\odot$, and display a projected separation of $\sim\!29$kpc and a physical separation of $\sim\!240$kpc. Evidence of ongoing star formation has been found in both galaxies, with neither one showing an enhanced star-formation rate that would be expected if they were already interacting. One galaxy displays a disturbed morphology but shows ordered gas rotation, which may reflect a previous minor merger event in the recent history of that system. The nearest spectroscopically confirmed neighbour lies at a distance of 38Mpc. These results indicate that these dwarf galaxies have no neighbouring massive galaxies, however with the data available we have been unable to determine whether these galaxies are isolated in the field or belong to a group of low-mass galaxies. As a detection of a rare dwarf-dwarf pair beyond the Local Universe, this system provides an uncommon opportunity to explore the properties of galaxy groups in the low-galaxy mass regime as a function of redshift.

The SAMI Galaxy Survey: Quenching of Star Formation in Clusters I. Transition Galaxies

Abstract We use integral-field spectroscopy from the SAMI Galaxy Survey to identify galaxies that show evidence of recent quenching of star formation. The galaxies exhibit strong Balmer absorption in the absence of ongoing star formation in more than 10% of their spectra within the SAMI field of view. These -strong (HDS) galaxies (HDSGs) are rare, making up only ∼2% (25/1220) of galaxies with stellar mass &gt; 10. The HDSGs make up a significant fraction of nonpassive cluster galaxies (15%; 17/115) and a smaller fraction (2.0%; 8/387) of the nonpassive population in low-density environments. The majority (9/17) of cluster HDSGs show evidence of star formation at their centers, with the HDS regions found in the outer parts of the galaxy. Conversely, the HDS signal is more evenly spread across the galaxy for the majority (6/8) of HDSGs in low-density environments and is often associated with emission lines that are not due to star formation. We investigate the location of the HDSGs in the clusters, finding that they are exclusively within 0.6R 200 of the cluster center and have a significantly higher velocity dispersion relative to the cluster population. Comparing their distribution in projected phase space to those derived from cosmological simulations indicates that the cluster HDSGs are consistent with an infalling population that has entered the central 0.5r 200,3D cluster region within the last ∼1 Gyr. In the eight of nine cluster HDSGs with central star formation, the extent of star formation is consistent with that expected of outside-in quenching by ram pressure stripping. Our results indicate that the cluster HDSGs are currently being quenched by ram pressure stripping on their first passage through the cluster.

Molecular gas in radio galaxies in dense megaparsec-scale environments at z = 0.4–2.6

Context. Low luminosity radio galaxies (LLRGs) typically reside in dense megaparsec-scale environments and are often associated with brightest cluster galaxies (BCGs). They are an excellent tool to study the evolution of molecular gas reservoirs in giant ellipticals, even close to the active galactic nucleus. Aims. We investigate the role of dense megaparsec-scale environment in processing molecular gas in LLRGs in the cores of galaxy (proto-)clusters. To this aim we selected within the COSMOS and DES surveys a sample of five LLRGs at z = 0.4−2.6 that show evidence of ongoing star formation on the basis of their far-infrared (FIR) emission. Methods. We assembled and modeled the FIR-to-UV spectral energy distributions (SEDs) of the five radio sources to characterize their host galaxies in terms of stellar mass and star formation rate. We observed the LLRGs with the IRAM-30 m telescope to search for CO emission. We then searched for dense megaparsec-scale overdensities associated with the LLRGs using photometric redshifts of galaxies and the Poisson Probability Method, which we have upgraded using an approach based on the wavelet-transform (wPPM), to ultimately characterize the overdensity in the projected space and estimate the radio galaxy miscentering. Color-color and color-magnitude plots were then derived for the fiducial cluster members, selected using photometric redshifts. Results. Our IRAM-30 m observations yielded upper limits to the CO emission of the LLRGs, at z = 0.39, 0.61, 0.91, 0.97, and 2.6. For the most distant radio source, COSMOS-FRI 70 at z = 2.6, a hint of CO(7→6) emission is found at 2.2σ. The upper limits found for the molecular gas content M(H2)/M⋆ &lt; 0.11, 0.09, 1.8, 1.5, and 0.29, respectively, and depletion time τdep ≲ (0.2−7) Gyr of the five LLRGs are overall consistent with the corresponding values of main sequence field galaxies. Our SED modeling implies large stellar-mass estimates in the range log(M⋆/M⊙) = 10.9−11.5, typical for giant ellipticals. Both our wPPM analysis and the cross-matching of the LLRGs with existing cluster/group catalogs suggest that the megaparsec-scale overdensities around our LLRGs are rich (≲1014 M⊙) groups and show a complex morphology. The color-color and color-magnitude plots suggest that the LLRGs are consistent with being star forming and on the high-luminosity tail of the red sequence. The present study thus increases the still limited statistics of distant cluster core galaxies with CO observations. Conclusions. The radio galaxies of this work are excellent targets for ALMA as well as next-generation telescopes such as the James Webb Space Telescope.

Star Formation Rates of Massive Molecular Clouds in the Central Molecular Zone

Abstract We investigate star formation at very early evolutionary phases in five massive clouds in the inner 500 pc of the Galaxy, the Central Molecular Zone (CMZ). Using interferometer observations of H2O masers and ultra-compact H ii regions, we find evidence of ongoing star formation embedded in cores of 0.2 pc scales and ≳105 cm−3 densities. Among the five clouds, Sgr C possesses a high (9%) fraction of gas mass in gravitationally bound and/or protostellar cores, and follows the dense (≳104 cm−3) gas star formation relation that is extrapolated from nearby clouds. The other four clouds have less than 1% of their cloud masses in gravitationally bound and/or protostellar cores, and star formation rates 10 times lower than predicted by the dense gas star formation relation. At the spatial scale of these cores, the star formation efficiency is comparable to that in Galactic disk sources. We suggest that the overall inactive star formation in these CMZ clouds could be because there is much less gas confined in gravitationally bound cores, which may be a result of the strong turbulence in this region and/or the very early evolutionary stage of the clouds when collapse has only recently started.

Stellar Proper Motions in the Orion Nebula Cluster

Abstract The Orion Nebula Cluster (ONC) is the nearest site of ongoing massive star formation, which allows us to study the kinematics and dynamics of the region in detail and constrain star formation theories. Using HST ACS/WFPC2/WFC3IR and Keck II NIRC2 data, we have measured the proper motions of 701 stars within an ∼6′ × 6′ field of view around the center of the ONC. We have found more than 10 escaping star candidates, concentrated predominantly at the core of the cluster. The proper motions of the bound stars are consistent with a normal distribution, albeit elongated north–south along the Orion filament, with proper-motion dispersions of mas yr−1 or intrinsic velocity dispersions of km s−1 assuming a distance of 400 pc to the ONC. The cluster shows no evidence for tangential-to-radial anisotropy. Our velocity dispersion profile agrees with the prediction from the observed stellar + gas density profile from Da Rio et al., indicating that the ONC is in virial equilibrium. This finding suggests that the cluster was formed with a low star formation efficiency per dynamical timescale based on comparisons with current star formation theories. Our survey also recovered high-velocity IR sources BN, x and n in the BN/KL region. The estimated location of the first two sources ∼500 yr ago agrees with that of the radio source I, consistent with their proposed common origin from a multistellar disintegration. However, source n appears to have a small proper motion and is unlikely to have been involved in the event.

Non-thermal emission resulting from a supernova explosion inside an extragalactic jet

Context. Core-collapse supernovae are found in galaxies with ongoing star-formation. In a starburst galaxy hosting an active galactic nucleus with a relativistic jet, supernovae can take place inside the jet. The collision of the supernova ejecta with the jet flow is expected to lead to the formation of an interaction region, in which particles can be accelerated and produce high-energy emission. Aims. We study the non-thermal radiation produced by electrons accelerated as a result of a supernova explosion inside the jet of an active galactic nucleus within a star-forming galaxy. Methods. We first analyzed the dynamical evolution of the supernova ejecta impacted by the jet. Then, we explored the parameter space using simple prescriptions for the observed gamma-ray lightcurve. Finally, the synchrotron and the inverse Compton spectral energy distributions for two types of sources, a radio galaxy and a powerful blazar, are computed. Results. For a radio galaxy, the interaction between a supernova and a jet of power ∼1043 − 1044 erg s−1 can produce apparent gamma-ray luminosities of ∼1042 − 1043 erg s−1, with an event duty cycle of supernova remnant interacting with the jet close to one for one galaxy. For a blazar with a powerful jet of ∼1046 erg s−1, the jet-supernova ejecta interaction could produce apparent gamma-ray luminosities of ∼1043 − 1044 erg s−1, but with a much lower duty cycle. Conclusions. The interaction of supernovae with misaligned jets of moderate power can be relatively frequent, and can result in steady gamma-ray emission potentially detectable for sources in the local universe. For powerful blazars much farther away, the emission would be steady as well, and it might be detectable under very efficient acceleration, but the events would be rather infrequent.

The Arecibo Pisces–Perseus Supercluster Survey. I. Harvesting ALFALFA

Abstract We report a multi-objective campaign of targeted 21 cm H i line observations of sources selected from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey and galaxies identified by their morphological and photometric properties in the Sloan Digital Sky Survey. The aims of this program have been (1) to confirm the reality of some ALFALFA sources whose enigmatic nature suggest additional multiwavelength observations; (2) to probe the low signal-to-noise ratio (S/N) regime, below the ALFALFA reliability limit; and (3) to explore the feasibility of using optical morphology, color, and surface brightness to identify gas-rich objects in the region of the Pisces–Perseus Supercluster (PPS) whose H i fluxes are below the ALFALFA sensitivity limit at that distance. As expected, the reliability of ALFALFA detections depends strongly on the S/N of the H i line signal and its coincidence with a probable stellar counterpart identified by its optical properties, suggestive of ongoing star formation. The identification of low-mass, star-forming populations enables targeted H i line observations to detect galaxies with H i line fluxes below the ALFALFA sensitivity limits in fixed local volumes (D &lt; 100 Mpc). The method explored here serves as the basis for extending the sample of gas-bearing objects as part of the ongoing Arecibo Pisces–Perseus Supercluster Survey (APPSS).

Gemini IFU, VLA, and HST observations of the OH Megamaser Galaxy IRAS17526 + 3253★

AbstractWe present a multiwavelength study of the OH megamaser galaxy IRAS17526 + 3253, based on new Gemini multi-object spectrograph integral field unit (GMOS/IFU) observations, Hubble Space Telescope F814W, and H α + [N ii] images, and archival 2MASS and 1.49 GHz VLA data. The Hubble Space Telescope(HST) images clearly reveal a mid-to-advanced stage major merger whose northwestern and southeastern nuclei have a projected separation of ∼8.5 kpc. Our HST/H α + [N ii] image shows regions of ongoing star formation across the envelope on ∼10 kpc scales, which are aligned with radio features, supporting the interpretation that the radio emission originates from star-forming regions. The measured H α luminosities imply that the unobscured star formation rate (SFR) is ∼10–30 M⊙ yr−1. The GMOS/IFU data reveal two structures in northwestern separated by 850 pc and by a discontinuity in the velocity field of ∼ 200 km s−1. We associate the blueshifted and redshifted components with, respectively, the distorted disc of northwestern and tidal debris, possibly a tail originating in southeastern. Star formation is the main ionization source in both components, which have SFRs of ∼2.6–7.9 M⊙ yr−1 and ∼1.5–4.5 M⊙ yr−1, respectively. Fainter line emission bordering these main components is consistent with shock ionization at a velocity ∼200 km s−1 and may be the result of an interaction between the tidal tail and the northwestern galaxy’s disc. IRAS17526 + 3253 is one of only a few systems known to host both luminous OH and H2O masers. The velocities of the OH and H2O maser lines suggest that they are associated with the northwestern and southeastern galaxies, respectively (Martin et al.; Wagner).

Ongoing star formation at the outskirts of Sextans A: Spectroscopic detection of early-O type stars.

With both nebular- and stellar-derived abundances of $\lesssim$ 1/10 Zsun and low foreground extinction, Sextans A is a prime candidate to replace the Small Magellanic Cloud as reservoir of metal-poor massive stars and reference to study the metal-poor Universe. We report the discovery of two early-O type stars in Sextans A, the earliest O-stars with metallicity < 1/7 Zsun known to date, and two additional O9 stars. Colour-excess estimates towards individual targets, enabled by spectral typing, manifest that internal reddening is neither uniform nor negligible. The four targets define a new region of star formation far from the optically-brightest centre of the galaxy and from its conspicuous HII shells, but not devoid of neutral hydrogen. In fact, we detect a spatial correlation between OB-stars and HI in Sextans A and other dIrr's that leads us to propose that the neutral phase may be fundamental to star formation in low-density environments. According to the existing evidence at least two of the targets formed in isolation, thus suggestive of an stochastic sampling of the initial mass function that would enable low-mass galaxies like Sextans A to form very massive stars. The discovery of these four stars provide spatially-resolved, spectroscopic confirmation of recent findings suggesting that dwarf galaxies can sustain star formation despite the low density of the gas phase.

Fast and energetic AGN-driven outflows in simulated dwarf galaxies

The systematic analysis of optical large-scale surveys has revealed a population of dwarf galaxies hosting AGN, which have been confirmed by X-ray follow-up observations. Recently, the MaNGA survey identified six dwarf galaxies that appear to have an AGN that is preventing on-going star formation. It is therefore timely to study the physical properties of dwarf galaxies, in particular whether the presence of an AGN can affect their evolution. Using the moving mesh code AREPO, we have investigated different models of AGN activity, ranging from simple energy-driven spherical winds to collimated, mass-loaded, bipolar outflows in high resolution simulations of isolated dwarf galaxies hosting an active black hole. Our simulations also include a novel implementation of star formation and mechanical supernova (SN) feedback. We find that AGN outflows have a small but systematic effect on the central star formation rates (SFRs) for all set-ups explored, while substantial effects on the global SFR are only obtained with strong SNe and a sustained high-luminosity AGN with an isotropic wind. This suggests that AGN feedback in dwarf galaxies is unlikely to directly regulate their global SFRs. There is, however, a significant effect on outflow properties, which are notably enhanced by the AGN to much higher outflow temperatures and velocities, in agreement with kinematic signatures from the MaNGA survey. This indicates that AGN may play an indirect role in regulating the baryon cycle in dwarf galaxies by hindering cosmic gas inflows.

Kinematics and dynamics of the luminous infrared galaxy pair NGC 5257/58 (Arp 240)

Context. Encounters between galaxies modify their morphology, kinematics, and star formation history. The relation between these changes and external perturbations is not straightforward. The great number of parameters involved requires both the study of large samples and individual encounters where particular features, motions, and perturbations can be traced and analysed in detail. Aims. We analysed the morphology, kinematics, and dynamics of two luminous infrared spiral galaxies of almost equal mass, NGC 5257 and NGC 5258, in which star formation is mostly confined to the spiral arms, in order to understand interactions between galaxies of equivalent masses and star-forming processes during the encounter. Methods. Using scanning Fabry–Perot interferometry, we studied the contribution of circular and non-circular motions and the response of the ionized gas to external perturbations. We compared the kinematics with direct images and traced the star-forming processes and gravitational effects due to the presence of the other galaxy. The spectral energy distribution of each member of the pair was fitted. A mass model was fitted to the rotation curve of each galaxy. Results. Large, non-circular motions detected in both galaxies are associated with a bar, spiral arms, and HII regions for the inner parts of the galaxies, and with the tidal interaction for the outer parts of the discs. Bifurcations in the rotation curves indicate that the galaxies have recently undergone pericentric passage. The pattern speed of a perturbation of one of the galaxies is computed. Location of a possible corotation seems to indicate that the gravitational response of the ionized gas in the outer parts of the disc is related to the regions where ongoing star formation is confined. The spectral energy distribution fit indicates slightly different star formation history for each member of the pair. For both galaxies, a pseudo-isothermal halo better fits the global mass distribution.

J1234+3901: an extremely metal-deficient compact star-forming dwarf galaxy at redshift 0.133

We have obtained optical spectroscopy of one of the most metal-poor dwarf star-forming galaxies (SFG) in the local Universe, J1234+3901, with the Large Binocular Telescope (LBT)/Multi-Object Dual Spectrograph (MODS). This blue compact dwarf (BCD) galaxy with a redshift z=0.133 was selected from the Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS). Its properties are extreme in many ways. Its oxygen abundance 12 + log O/H = 7.035+/-0.026 is among the lowest ever observed for a SFG. Its absolute magnitude Mg = -17.35 mag makes it the brightest galaxy among the known BCDs with 12 + log O/H < 7.3. With its low metallicity, low stellar mass M* = 10^7.13 Msun and very low mass-to-light ratio M*/Lg ~ 0.01 (in solar units), it deviates strongly from the mass-metallicity and luminosity-metallicity relations defined by the bulk of the SFGs in SDSS DR14. J1234+3901 has a very high specific star-formation rate sSFR ~ 100 Gyr^-1, indicating very active ongoing star-formation. Its spectrum shows a strong HeII 4686 emission line, with a flux ~ 2.4 per cent that of the Hbeta emission line. The most probable source of ionizing radiation for producing such a strong line is fast radiative shocks. J1234+3901 has a ratio O32 = [OIII]5007/[OII]3727 ~ 15, the highest among the lowest-metallicity SFGs, and is thus likely leaking Lyman continuum radiation. It is a good candidate for being a young dwarf galaxy, with a large fraction of its stars formed recently. As such, it is probably one of the best local counterparts of dwarf primeval galaxies responsible for the reionization of the early Universe.

Investigating Inner and Large-scale Physical Environments of IRAS 17008-4040 and IRAS 17009-4042 toward L = 345.°5, B = 0.°3

We present a multi-wavelength observational study of IRAS 17008-4040 and IRAS 17009-4042 to probe the star-formation (SF) mechanisms operational in both the sites. Each IRAS site is embedded within a massive ATLASGAL 870 micron clump (~2430 - 2900 M_sun), and several parsec-scale filaments at 160 micron are radially directed toward these clumps (at T_d ~ 25 - 32 K). The analysis of the Spitzer and VVV photometric data depicts a group of infrared-excess sources toward both the clumps, suggesting the ongoing SF activities. In each IRAS site, high-resolution GMRT radio maps at 0.61 and 1.28 GHz confirm the presence of H II regions, which are powered by B-type stars. In the site IRAS 17008-4040, a previously known O-star candidate without an H II region is identified as an infrared counterpart of the 6.7 GHz methanol maser emission (i.e. IRcmme). Based on the VLT/NACO adaptive-optics L' image (resolution ~ 0.1 arcsec), the source IRcmme is resolved into two objects (i.e. IRcmme1 and IRcmme2) within a scale of 900 AU that are found to be associated with the ALMA core G345.50M. IRcmme1 is characterized as the main accreting HMPO candidate before the onset of an ultracompact H II region. In the site IRAS 17009-4042, the 1.28 GHz map has resolved two radio sources that were previously reported as a single radio peak. Altogether, in each IRAS site, the junction of the filaments (i.e. massive clump) is investigated with the cluster of infrared-excess sources and the ongoing massive SF. These evidences are consistent with the "hub-filament" systems as proposed by Myers (2009).

SUPER

Theoretical models of galaxy formation suggest that the presence of an active galactic nucleus (AGN) is required to regulate the growth of its host galaxy through feedback mechanisms, produced by, for example, AGN-driven outflows. Although many observational studies have revealed that such outflows are common both at low and high redshift, a comprehensive picture is still missing. In particular, the peak epoch of galaxy assembly (1 &lt; z &lt; 3) has been poorly explored so far, and current observations in this redshift range are mostly limited to targets with high chances to be in an outflowing phase. This paper introduces SUPER (a SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback), an ongoing ESO’s VLT/SINFONI Large Programme. SUPER will perform the first systematic investigation of ionized outflows in a sizeable and blindly-selected sample of 39 X-ray AGN at z ∼ 2, which reaches high spatial resolutions (∼2 kpc) thanks to the adaptive optics-assisted IFS observations. The outflow morphology and star formation in the host galaxy will be mapped through the broad component of [O III]λ5007 and the narrow component of Hα emission lines. The main aim of our survey is to infer the impact of outflows on the on-going star formation and to link the outflow properties to a number of AGN and host galaxy properties. We describe here the survey characteristics and goals, as well as the selection of the target sample. Moreover, we present a full characterization of its multi-wavelength properties: we measure, via spectral energy distribution fitting of UV-to-FIR photometry, stellar masses (4 × 109 − 2 × 1011 M⊙), star formation rates (25 − 680 M⊙ yr−1) and AGN bolometric luminosities (2 × 1044 − 8 × 1047 erg s−1), along with obscuring column densities (up to 2 × 1024 cm−2) and luminosities in the hard 2 − 10 keV band (2 × 1043 − 6 × 1045 erg s−1) derived through X-ray spectral analysis. Finally, we classify our AGN as jetted or non-jetted according to their radio and FIR emission.

A tiny host galaxy for the first giant black hole:z = 7.5 quasar in BlueTides

The most distant known quasar recently discovered by Ba\~nados et al. (2018) is at $z=7.5$ (690 Myr after the Big Bang), at the dawn of galaxy formation. We explore the host galaxy of the brightest quasar in the large volume cosmological hydrodynamic simulation BlueTides, which in Phase II has reached these redshifts. The brightest quasar in BlueTides has a luminosity of a $\sim$ few $10^{13} L_{\odot}$ and a black hole mass of $6.4 \times 10^{8} M_{\odot}$ at $z \sim 7.5$, comparable to the observed quasar (the only one in this large volume). The quasar resides in a rare halo of mass $M_{H} \sim 10^{12} M_{\odot}$ and has a host galaxy of stellar mass of $4 \times 10^{10}M_{\odot}$ with an ongoing (intrinsic) star formation rate of $\sim 80 M_{\odot} yr^{-1}$. The corresponding intrinsic UV magnitude of the galaxy is $-23.1$, which is roughly $2.7$ magnitudes fainter than the quasar's magnitude of $-25.9$. We find that the galaxy is highly metal enriched with a mean metallicity equal to the solar value. We derive quasar and galaxy spectral energy distribution (SED) in the mid and near infrared JWST bands. We predict a significant amount of dust attenuation in the rest-frame UV corresponding to $A_{1500} \sim 1.7$ giving an UV based SFR of $\sim 14 M_{\odot} yr^{-1}$. We present mock JWST images of the galaxy with and without central point source, in different MIRI and NIRCam filters. The host galaxy is detectable in NIRCam filters, but it is extremely compact ($R_{E}=0.35$ kpc). It will require JWST's exquisite sensitivity and resolution to separate the galaxy from the central point source. Finally within the FOV of the quasar in BlueTides there are two more sources that would be detectable by JWST.