Parsec Research Articles

Unveiling dust, molecular gas, and high star-formation efficiency in extremely UV bright star-forming galaxies at z ~ 2.1-3.6

We analysed the Atacama Large Millimetre/submillimetre Array (ALMA) far-infrared (FIR), 1.3 mm, dust continuum and CO emission of 12 starburst galaxies at $z 2.1-3.6$ selected for their extreme brightness in the rest-frame UV, with absolute magnitudes of $-23.4$ to $-24.7$. We also analysed their Very Large Telescope (VLT) High Acuity Wide field $K$-band Imager (HAWK-I) $H$- and s $-band images. The targeted galaxies are characterised by negligible dust attenuations with blue UV spectral slopes ($-2.62$ to $-1.84$), very young stellar populations of $ 10$ Myr, and powerful starbursts with a high mean specific star-formation rate of $ $, placing them $ 1.5$ dex above the main sequence at similar redshifts and stellar masses stars odot $). The FIR dust continuum emission revealed in nine galaxies gives IR luminosities of $(5.9-28.3) L_ odot $, with six galaxies remaining dominated by unobscured UV star-formation rates, and high dust masses barely produced by supernovae within the 10 Myr timescale. The CO emission detected in eight galaxies leads to molecular gas masses higher than stellar masses, with the mean molecular gas mass fraction as high as $82<!PCT!>$. The corresponding star-formation efficiencies reach $ 40$<!PCT!>, with amazingly short molecular gas depletion timescales between less than 13 Myr and 71 Myr. These unique properties never reported in previously studied galaxies highlight that these galaxies are likely caught at the very beginning of their stellar mass build-up and undergo a very efficient and fast conversion of gas into stars that can only result from the gas collapse within a very short free-fall time. We find that the feedback-free starburst model seems to be able to explain the formation of these galaxies. To reconcile the co-spatial FIR dust emission with the UV-bright unattenuated emission, we speculate about the presence of radiation-driven outflows that can temporarily remove dust at the location of the starburst and expel it at large distances in line with the measured high FIR effective radii (1.7 kpc to 5 kpc) in comparison to the very compact stellar radii that are a few hundreds of parsecs).

JADES: Spectroscopic Confirmation and Proper Motion for a T-Dwarf at 2 kpc

Large area observations of extragalactic deep fields with the James Webb Space Telescope (JWST) have provided a wealth of candidate low-mass L- and T-class brown dwarfs. The existence of these sources, which are at derived distances of hundreds of parsecs to several kiloparsecs from the Sun, has strong implications for the low-mass end of the stellar initial mass function, and the link between stars and planets at low metallicities. In this letter, we present a JWST/NIRSpec PRISM spectrum of brown dwarf JADES-GS-BD-9, confirming its photometric selection from observations taken as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. Fits to this spectrum indicate that the brown dwarf has an effective temperature of 800–900 K (T5–T6) at a distance of 1.8–2.3 kpc from the Sun, with evidence of the source being at low metallicity ([M/H] ≤ −0.5). Finally, because of the cadence of JADES NIRCam observations of this source, we additionally uncover a proper motion between the 2022 and 2023 centroids, and we measure a proper motion of 20 ± 4 mas yr−1 (a transverse velocity of 214 km s−1 at 2.25 kpc). At this predicted metallicity, distance, and transverse velocity, it is likely that this source belongs either to the edge of the Milky Way thick disk or the galactic halo. This spectral confirmation demonstrates the efficacy of photometric selection of these important sources across deep extragalactic JWST imaging.

Implications for Galactic Electron Density Structure from Pulsar Sightlines Intersecting H ii Regions

Recent radio surveys have revealed pulsars with dispersion and scattering delays induced by ionized gas that are larger than the rest of the observed pulsar population, in some cases with electron column densities (or dispersion measures, DMs) larger than the maximum predictions of Galactic electron density models. By cross-matching the observed pulsar population against H ii region catalogs, we show that the majority of pulsars with DM > 600 pc cm−3 and scattering delays τ(1 GHz) > 10 ms lie behind H ii regions, and that H ii region intersections may be relevant to as much as a third of the observed pulsar population. The fraction of the full pulsar population with sightlines intersecting H ii regions is likely larger. Accounting for H ii regions resolves apparent discrepancies where Galactic electron density models place high-DM pulsars beyond the Galactic disk. By comparing emission measures inferred from recombination line observations to pulsar DMs, we show that H ii regions can contribute tens to hundreds of parsecs per cubic centimeter in electron column density along a pulsar line of sight. We find that nearly all pulsars with significant excess (and deficit) scattering from the mean τ–DM relation are spatially coincident with known discrete ionized gas structures, including H ii regions. Accounting for H ii regions is critical to the interpretation of radio dispersion and scattering measurements as electron density tracers, both in the Milky Way and in other galaxies.

A pilot study of Galactic radio recombination lines using FAST: Identification of diffuse ionized gas clumps and off-arm star-forming regions

Observing low-frequency decimeter hydrogen radio recombination lines (RRLs) with large single-dish telescopes, such as the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the L band, is a unique method for probing massive star formation on scales of hundreds of parsecs. This approach is particularly effective for detecting relatively weak and extended emissions from low-density gas ionized by massive stars. Deep, unbiased decimeter or centimeter RRL surveys with large single-dish telescopes can significantly enhance our understanding of the diffuse ionized gas along the Galactic plane. This, in turn, will improve our knowledge of the life cycle of matter in the interstellar medium and the dynamics of the Galaxy. In this context, we present a pilot project for such a blind L-band RRL survey targeting the Galactic plane and conducted using FAST. The results include the detection of RRL clumps and the identification of an off-arm active massive star-forming region near the Sagittarius-Carina arm. The ongoing and upcoming massive star formation in this region may be associated with the kink in the Sagittarius-Carina arm near 23$^ circ $ azimuth.

On the Origin of the X-Ray Emission in Heavily Obscured Compact Radio Sources

X-ray continuum emission of active galactic nuclei (AGNs) may be reflected by circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray frequencies. Here, we discuss the broadband emission of three radio-loud AGNs belonging to the class of compact symmetric objects (CSOs), with detected narrow Fe Kα lines. CSOs have newly born radio jets, forming compact radio lobes with projected linear sizes of the order of a few to hundreds of parsecs. We model the radio-to-γ-ray spectra of compact lobes in J1407+2827, J1511+0518, and J2022+6137, which are among the nearest and the youngest CSOs known to date, and are characterized by an intrinsic X-ray absorbing column density of N H > 1023 cm−2. In addition to the archival data, we analyze the newly acquired Chandra X-ray Observatory and Submillimeter Array (SMA) observations, and also refine the γ-ray upper limits from Fermi Large Area Telescope monitoring. The new Chandra data exclude the presence of the extended X-ray emission components on scales larger than 1.″5. The SMA data unveil a correlation between the spectral index of the electron distribution in the lobes and N H, which can explain the γ-ray quietness of heavily obscured CSOs. Based on our modeling, we argue that the inverse-Compton emission of compact radio lobes may account for the intrinsic X-ray continuum in all these sources. Furthermore, we propose that the observed iron lines may be produced by a reflection of the lobes’ continuum from the surrounding cold dust.

The Accretion Mode in Sub-Eddington Supermassive Black Holes: Getting into the Central Parsecs of Andromeda

The inner kiloparsec regions surrounding sub-Eddington (luminosity less than 10−3 in Eddington units, L Edd) supermassive black holes (BHs) often show a characteristic network of dust filaments that terminate in a nuclear spiral in the central parsecs. Here we study the role and fate of these filaments in one of the least accreting BHs known, M31 (10−7 L Edd) using hydrodynamical simulations. The evolution of a streamer of gas particles moving under the barred potential of M31 is followed from kiloparsec distance to the central parsecs. After an exploratory study of initial conditions, a compelling fit to the observed dust/ionized gas morphologies and line-of-sight velocities in the inner hundreds of parsecs is produced. After several million years of streamer evolution, during which friction, thermal dissipation, and self-collisions have taken place, the gas settles into a disk tens of parsecs wide. This is fed by numerous filaments that arise from an outer circumnuclear ring and spiral toward the center. The final configuration is tightly constrained by a critical input mass in the streamer of several 103 M ☉ (at an injection rate of 10−4 ); values above or below this lead to filament fragmentation or dispersion respectively, which are not observed. The creation of a hot gas atmosphere in the region of ∼106 K is key to the development of a nuclear spiral during the simulation. The final inflow rate at 1 pc from the center is ∼1.7 × 10−7 M ☉ yr−1, consistent with the quiescent state of the M31 BH.

Dissecting the interstellar medium of a z = 6.3 galaxy

The study of the properties of galaxies in the first billion years after the Big Bang is one of the major topics of current astrophysics. Optical and near-infrared spectroscopy of the afterglows of long gamma-ray bursts (GRBs) provides a powerful diagnostic tool to probe the interstellar medium (ISM) of their host galaxies and foreground absorbers, even up to the highest redshifts. We analyze the VLT/X-shooter afterglow spectrum of GRB 210905A, triggered by the Neil Gehrels Swift Observatory, and detect neutral hydrogen, low-ionization, high-ionization, and fine-structure absorption lines from a complex system at z = 6.3118, which we associate with the GRB host galaxy. We use them to study the ISM properties of the host system, revealing the metallicity, kinematics, and chemical abundance pattern of its gas along the GRB line of sight. We also detect absorption lines from at least two foreground absorbers at z = 5.7390 and z = 2.8296. The total metallicity of the z ∼ 6.3 system is [M/H]tot = −1.72 ± 0.13, after correcting for dust depletion and taking α-element enhancement into account, as suggested by our analysis. This is consistent with the values found for the other two GRBs at z ∼ 6 with spectroscopic data showing metal absorption lines (GRB 050904 and GRB 130606A), and it is at the higher end of the metallicity distribution of quasar damped Lyman-α systems (QSO-DLAs) extrapolated to such a high redshift. In addition, we determine the overall amount of dust and dust-to-metal mass ratio (DTM) ([Zn/Fe]fit = 0.33 ± 0.09 and DTM = 0.18 ± 0.03). We find indications of nucleosynthesis due to massive stars and, for some of the components of the gas clouds, we find evidence of peculiar nucleosynthesis, with an overabundance of aluminum (as also found for GRB 130606A). From the analysis of fine-structure lines, we determine distances of several kiloparsecs for the low-ionization gas clouds closest to the GRB. Those are farther distances than usually found for GRB host absorption systems, possibly due to the very high number of ionizing photons produced by the GRB that could ionize the line of sight up to several hundreds of parsecs. Using the HST/F140W image of the GRB field, we show the GRB host galaxy (with a possible afterglow contamination) as well as multiple objects within 2″ from the GRB position. We discuss the galaxy structure and kinematics that could explain our observations, also taking into account a tentative detection of Lyman-α emission at z = 6.3449 (∼1200 km s−1 from the GRB redshift in velocity space), and the observational properties of Lyman-α emitters at very high redshift. This study shows the amazing potential of GRBs to access detailed information on the properties (metal enrichment, gas kinematic, dust content, nucleosynthesis...) of very high-redshift galaxies, independently of the galaxy luminosity. Deep spectroscopic observations with VLT/MUSE and JWST will offer the unique possibility of combining the information presented in this paper with the properties of the ionized gas, with the goal of better understanding how galaxies in the reionization era form and evolve.

H i filaments as potential compass needles? Comparing the magnetic field structure of the Small Magellanic Cloud to the orientation of GASKAP-H i filaments

ABSTRACT High-spatial-resolution H i observations have led to the realization that the nearby (within few hundreds of parsecs) Galactic atomic filamentary structures are aligned with the ambient magnetic field. Enabled by the high-quality data from the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope for the Galactic ASKAP H i survey, we investigate the potential magnetic alignment of the $\gtrsim\!{10}\, {\rm pc}$-scale H i filaments in the Small Magellanic Cloud (SMC). Using the Rolling Hough Transform technique that automatically identifies filamentary structures, combined with our newly devised ray-tracing algorithm that compares the H i and starlight polarization data, we find that the H i filaments in the north-eastern end of the SMC main body (‘Bar’ region) and the transition area between the main body and the tidal feature (‘Wing’ region) appear preferentially aligned with the magnetic field traced by starlight polarization. Meanwhile, the remaining SMC volume lacks starlight polarization data of sufficient quality to draw any conclusions. This suggests for the first time that filamentary H i structures can be magnetically aligned across a large spatial volume ($\gtrsim\!{\rm kpc}$) outside of the Milky Way. In addition, we generate maps of the preferred orientation of H i filaments throughout the entire SMC, revealing the highly complex gaseous structures of the galaxy likely shaped by a combination of the intrinsic internal gas dynamics, tidal interactions, and star-formation feedback processes. These maps can further be compared with future measurements of the magnetic structures in other regions of the SMC.

The need for multicomponent dust attenuation in modeling nebular emission: Constraints from SDSS-IV MaNGA

A fundamental assumption adopted in nearly every extragalactic study that analyzes optical emission lines is that the attenuation of different emission lines can be described by a single attenuation curve, scaled by a single reddening parameter, usually E(B − V). Here we show this assumption fails in many cases with important implications for derived results. We developed a new method to measure the differential nebular attenuation among three kinds of transitions: the Balmer lines of hydrogen; high-ionization transitions (> 13.6 eV) including [Ne III], [O III], and [S III]; and low-ionization transitions (≲13.6 eV) including [O II], [N II], and [S II]. This method bins the observed data in a multidimensional space spanned by attenuation-insensitive line ratios. Within each small bin, the variations in nebular parameters such as the metallicity and ionization parameter are negligible compared to the variation in the nebular attenuation. This allowed us to measure the nebular attenuation using both forbidden lines and Balmer lines. We applied this method to a sample of 2.4 million star-forming (SF) spaxels from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. We found that the attenuation of high ionization lines and Balmer lines can be well described by a single Fitzpatrick (1999, PASP, 111, 63) extinction curve with RV = 3.1. However, no single attenuation curve can simultaneously account for these transitions and the derived attenuation of low-ionization lines. This strongly suggests that different lines have different effective attenuations, likely because spectroscopy at hundreds of parsecs to kiloparsecs of resolution mixes multiple physical regions that exhibit different intrinsic line ratios and different levels of attenuation. As a result, the assumption that different lines follow the same attenuation curve breaks down. Using a single attenuation curve determined by Balmer lines to correct attenuation-sensitive forbidden line ratios could bias the nebular parameters derived by 0.06–0.25 dex at AV = 1, depending on the details of the dust attenuation model. Observations of a statistically large sample of H II regions with high spatial resolutions and large spectral coverage are vital for improved modeling and deriving accurate corrections for this effect.

Improving black hole accretion treatment in hydrodynamical simulations

ABSTRACT The large-Galactic scales are connected to the many orders of magnitude smaller supermassive black hole (SMBH) scales by an episodic cycle of feeding and feedback. Active Galactic nuclei (AGN) are powered by accretion on to SMBH and the majority of AGN energy in near-Eddington regime is produced in thin subpc accretion discs. Currently, it is very difficult to model processes that occur on vastly different scales, ranging from the circumnuclear gas reservoirs at tens to hundreds of parsecs down to the accretion disc scales at <0.01 pc. While subgrid prescriptions used in large-scale or cosmological simulations are able to reproduce large-scale feedback, we propose using a more realistic model in parsec-scale simulations, where it is important to get accurate time-scales to understand how feedback affects gas dynamics and star formation in the vicinity of the AGN. To test our approach we use a subresolution thin accretion disc model coupled to the SMBH in a set of hydrodynamical simulations of a retrograde collision between a gas ring and a molecular cloud in an environment similar to the Galactic Centre using the SPH code Gadget-3. The disc-mediated feeding of the SMBH is relatively smooth and delayed compared to an instantaneous feeding prescription. While the reduction of accretion due to feedback is present in both accretion disc and instantaneous feeding simulations, a clear central cavity appears only in accretion disc runs – hinting that a less volatile accretion phase could have a greater impact on the surrounding gas.

A GALAH view of the chemical homogeneity and ages of stellar strings identified in Gaia

ABSTRACT The advent of Gaia has led to the discovery of nearly 300 elongated stellar associations (called ‘strings’) spanning hundreds of parsecs in length and mere tens of parsecs in width. These newfound populations present an excellent laboratory for studying the assembly process of the Milky Way thin disc. In this work, we use data from GALAH DR3 to investigate the chemical distributions and ages of 18 newfound stellar populations, 10 of which are strings and 8 of which are compact in morphology. We estimate the intrinsic abundance dispersions in [X/H] of each population and compare them with those of both their local fields and the open cluster (OC) M 67. We find that all but one of these groups are more chemically homogeneous than their local fields. Furthermore, half of the strings, namely Theias 139, 169, 216, 303, and 309, have intrinsic [X/H] dispersions that range between 0.01 and 0.07 dex in most elements, equivalent to those of many OCs. These results provide important new observational constraints on star formation and the chemical homogeneity of the local interstellar medium (ISM). We investigate each population’s Li and chemical clock abundances (e.g. [Sc/Ba], [Ca/Ba], [Ti/Ba], and [Mg/Y]) and find that the ages suggested by chemistry generally support the isochronal ages in all but six structures. This work highlights the unique advantages that chemistry holds in the study of kinematically related stellar groups.

Jet propagation through inhomogeneous media and shock ionization

AbstractIn this contribution, we present the first numerical simulations of a relativistic outflow propagating through the inner hundreds of parsecs of its host galaxy, including atomic and ionized hydrogen, and the cooling effects of ionization. Our results are preliminary, but we observe efficient shock ionization of atomic hydrogen in interstellar clouds. The mean density of the interstellar medium in these initial simulations is lower than that expected in typical galaxies, which makes cooling times longer and thus no recombination is observed inside the shocked region. The velocities achieved by the shocked gas in the simulations are in agreement with observational results, although with a wide spectrum of values.

The Physics of the Coronal-line Region for Galaxies in Mapping Galaxies at Apache Point Observatory

Abstract The fundamental nature and extent of the coronal-line region (CLR), which may serve as a vital tracer for active galactic nucleus (AGN) activity, remain unresolved. Previous studies suggest that the CLR is produced by AGN-driven outflows and occupies a distinct region between the broad-line region and the narrow-line region, which places it tens to hundreds of parsecs from the galactic center. Here, we investigate 10 coronal line (CL; ionization potential ≳100 eV) emitting galaxies from the Sloan Digital Sky Survey IV Mapping Galaxies at Apache Point Observatory (MaNGA) catalog with emission from one or more CLs detected at ≥5σ above the continuum in at least 10 spaxels—the largest such MaNGA catalog. We find that the CLR is far more extended, reaching out to 1.3–23 kpc from the galactic center. We crossmatch our sample of 10 CL galaxies with the largest existing MaNGA AGN catalog and identify seven in it; two of the remaining three are galaxy mergers and the final one is an AGN candidate. Further, we measure the average CLR electron temperatures as ranging between 12,331 and 22,530 K, slightly above the typical threshold for pure AGN photoionization (∼20,000 K) and indicative of shocks (e.g., merger induced or from supernova remnants) in the CLR. We reason that ionizing photons emitted by the central continuum source (i.e., AGN photoionization) primarily generate the CLs, and that energetic shocks are an additional ionization mechanism that likely produce the most extended CLRs we measure.

Merging timescale for the supermassive black hole binary in interacting galaxy NGC 6240

Context. One of the mechanisms leading to the creation of a supermassive black hole (SMBH) is the so-called hierarchical merging scenario. Central SMBHs at the final phase of interacting and coalescing host-galaxies are observed as SMBH binary (SMBHB) candidates at different separations from hundreds of parsecs to megaparsecs. Aims. Today one of the strongest SMBHB candidates is the ultraluminous infrared galaxy NGC 6240 which was spatially and spectroscopically resolved in X-rays by Chandra. Dynamical calculation of central SMBHBs merging in a dense stellar environment allows us to retrace their evolution from kiloparsec to megaparsec scales. The main goal of our dynamical modeling was to reach the final, gravitational wave emission regime for the model BHs. Methods. We present direct N-body simulations with up to one million particles and relativistic post-Newtonian corrections for the SMBH particles up to 3.5 post-Newtonian terms. Results. Generally speaking, the set of initial physical conditions can strongly affect our merging time estimations. However, within a certain range of our parameters, we do not find any strong correlation between merging time and BH-to-BH mass or BH-to-bulge mass ratios. Varying the numerical parameters (like particle number – N) does not significantly change the merging time limits. From our 20 models, we find an upper limit on the merging time for central SMBHBs of less than ∼55 Myr. This precise number is only valid for our combination of initial mass ratios. Conclusions. Further detailed research of rare dual and multiple BHs in dense stellar environments (based on observational data) could clarify the dynamical co-evolution of central BHs and their host-galaxies.

The Galactic center chimneys: the base of the multiphase outflow of the Milky Way

Context.Outflows and feedback are key ingredients of galaxy evolution. Evidence for an outflow arising from the Galactic center (GC) – the so-called GC chimneys – has recently been discovered at radio, infrared, and X-ray bands.Aims.We undertake a detailed examination of the spatial relationships between the emission in the different bands in order to place constraints on the nature and history of the chimneys and to better understand their impact on the GC environment and their relation with Galactic scale outflows.Methods.We compare X-ray, radio, and infrared maps of the central few square degrees.Results.The X-ray, radio, and infrared emissions are deeply interconnected, affecting one another and forming coherent features on scales of hundreds of parsecs, therefore indicating a common physical link associated with the GC outflow. We debate the location of the northern chimney and suggest that it might be located on the front side of the GC because of a significant tilt of the chimneys toward us. We report the presence of strong shocks at the interface between the chimneys and the interstellar medium, which are traced by radio and warm dust emission. We observe entrained molecular gas outflowing within the chimneys, revealing the multiphase nature of the outflow. In particular, the molecular outflow produces a long, strong, and structured shock along the northwestern wall of the chimney. Because of the different dynamical times of the various components of the outflow, the chimneys appear to be shaped by directed large-scale winds launched at different epochs. The data support the idea that the chimneys are embedded in an (often dominant) vertical magnetic field, which likely diverges with increasing latitude. We observe that the thermal pressure associated with the hot plasma appears to be smaller than the ram pressure of the molecular outflow and the magnetic pressure. This leaves open the possibility that either the main driver of the outflow is more powerful than the observed hot plasma, or the chimneys represent a “relic” of past and more powerful activity.Conclusions.These multiwavelength observations corroborate the idea that the chimneys represent the channel connecting the quasi-continuous, but intermittent, activity at the GC with the base of theFermibubbles. In particular, the prominent edges and shocks observed in the radio and mid-infrared bands testify to the most powerful, more recent outflows from the central parsecs of the Milky Way.

Nonuniversal Interstellar Density Spectra Probed by Pulsars

Abstract Galactic interstellar turbulence affects density distribution and star formation. We introduce a new method of measuring interstellar turbulent density spectra by using the dispersion measures (DMs) of a large sample of pulsars. Without the need of invoking multiple tracers, we obtain nonuniversal density spectra in the multiphase interstellar medium over different ranges of length scales. By comparing the analytical structure function of DMs with the observationally measured one in different areas of sky, we find a shallow density spectrum arising from the supersonic turbulence in cold interstellar phases, and a Kolmogorov-like density spectrum in the diffuse warm ionized medium (WIM). Both spectra extend up to hundreds of parsecs. On larger scales, we identify, for the first time, a steep density spectrum in the diffuse WIM extending up to several kiloparsecs. Our results show that the DMs of pulsars can provide unique new information on the interstellar turbulence.

Mapping the ionized gas of the metal-poor H ii galaxy PHL 293B with MEGARA

ABSTRACT Here we report the first spatially resolved spectroscopic study for the galaxy PHL 293B using the high-resolution GTC/MEGARA integral field unit (IFU). PHL 293B is a local, extremely metal-poor, high ionization galaxy. This makes PHL 293B an excellent analogue for galaxies in the early Universe. The MEGARA aperture (∼ 12.5 arcsec × 11.3 arcsec) covers the entire PHL 293B main body and its far-reaching ionized gas. We created and discussed maps of all relevant emission lines, line ratios, and physical–chemical properties of the ionized ISM. The narrow emission gas appears to be ionized mainly by massive stars according to the observed diagnostic line ratios, regardless of the position across the MEGARA aperture. We detected low intensity broad emission components and blueshifted absorptions in the Balmer lines (H α,H β) which are located in the brightest zone of the galaxy ISM. A chemically homogeneity, across hundreds of parsecs, is observed in O/H. We take the oxygen abundance 12+log (O/H) = 7.64 ± 0.06 derived from the PHL 293B integrated spectrum as the representative metallicity for the galaxy. Our IFU data reveal for the first time that the nebular He iiλ4686 emission from PHL 293B is spatially extended and coincident with the ionizing stellar cluster, and allow us to compute its absolute He ii ionizing photon flux. Wolf-Rayet bumps are not detected excluding therefore Wolf-Rayet stars as the main He ii excitation source. The origin of the nebular He iiλ4686 is discussed.

Virtual Reality Headset Implementation on Parsec Cloud Gaming Platform

Virtual reality (VR) based games are a type of game that provides immersive gaming experience, allowing players to dive into the virtual world of the game being played. VR-based games require a high minimum computer specification, so thin clients cannot play VR-based games properly. This research aims to see how to enable thin computers to play VR-based games by utilizing cloud gaming technology. Using a high specification computer as a server, an android device as a VR headset, this Final Project implements a VR headset device so that it can be used in conjunction with cloud gaming services to be able to play VR-based games on thin computers and see how well the implementation by seeing the result from computer resources used and the Quality of Services. With Parsec cloud gaming services, the application carried out in this Final Project can run well on computers with low specifications. CPU usage on the client computer when the service is running is high at 91% usage, with 2818 MB RAM usage. Quality of Service is obtained when setting the highest quality preset, with a throughput of 16MB with a delay of about 2 ms. VR games that are played can run well with a minimum bandwidth of 15 Mbps selected from the Frame per Second (FPS) results obtained to reach 56 FPS with medium quality settings.

X-ray absorption in INTEGRAL active galactic nuclei

In this work the INTEGRAL hard X-ray selected sample of active galactic nuclei (AGN) has been used to investigate the possible contribution of absorbing material distributed within the host galaxies to the total amount of NH measured in the X-ray band. We collected all the available axial ratio measurements of the galaxies hosting our AGN together with their morphological information and found that for our hard X-ray selected sample as well there is a deficit of edge-on galaxies hosting type 1 AGN. We estimate that in our hard X-ray selected sample there is a deficit of 24% (±5%) of type 1 AGN. Possible bias in redshift has been excluded, as we found the same effect in a well-determined range of z where the number and the distributions of the two classes are statistically the same. Our findings clearly indicate that material located in the host galaxy on scales of hundreds of parsecs and not aligned with the putative absorbing torus of the AGN can contribute to the total amount of column density. This galactic absorber could be large enough to hide the broad line region of some type 1 AGN, thus causing their classification as type 2 objects and giving rise to the deficiency of type 1 objects in edge-on galaxies.

How runaway stars boost galactic outflows

ABSTRACT Roughly 10 per cent of OB stars are kicked out of their natal clusters before ending their life as supernovae. These so-called runaway stars can travel hundreds of parsecs into the low-density interstellar medium, where momentum and energy from stellar feedback is efficiently deposited. In this work, we explore how this mechanism affects large-scale properties of the galaxy, such as outflows. To do so we use a new model that treats OB stars and their associated feedback processes on a star-by-star basis. With this model, we compare two hydrodynamical simulations of Milky Way-like galaxies, one where we include runaways, and one where we ignore them. Including runaway stars leads to twice as many supernovae explosions in regions with gas densities ranging from $10^{-5}\, \mathrm{\,cm^{-3}}$ to $10^{-3}\, \mathrm{\,cm^{-3}}$. This results in more efficient heating of the inter-arm regions, and drives strong galactic winds with mass loading factors boosted by up to one order of magnitude. These outflows produce a more massive and extended multiphase circumgalactic medium, as well as a population of dense clouds in the halo. Conversely, since less energy and momentum is released in the dense star-forming regions, the cold phase of the interstellar medium is less disturbed by feedback effects.