Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at $$ \sqrt{s} $$, $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.

Multiphase feedback processes in the Sy2 galaxy NGC 5643

We study the multiphase feedback processes in the central ∼3 kpc of the barred Seyfert 2 galaxy NGC 5643. We used observations of the cold molecular gas (ALMA CO(2−1) transition) and ionized gas (MUSE IFU optical emission lines). We studied different regions along the outflow zone, which extends out to ∼2.3 kpc in the same direction (east-west) as the radio jet, as well as nuclear and circumnuclear regions in the host galaxy disk. The CO(2−1) line profiles of regions in the outflow and spiral arms show two or more different velocity components: one associated with the host galaxy rotation, and the others with out- or inflowing material. In the outflow region, the [O III]λ5007 Å emission lines have two or more components: the narrow component traces rotation of the gas in the disk, and the others are related to the ionized outflow. The deprojected outflowing velocities of the cold molecular gas (median Vcentral ∼ 189 km s−1) are generally lower than those of the outflowing ionized gas, which reach deprojected velocities of up to 750 km s−1 close to the active galactic nucleus (AGN), and their spatial profiles follow those of the ionized phase. This suggests that the outflowing molecular gas in the galaxy disk is being entrained by the AGN wind. We derive molecular and ionized outflow masses of ∼5.2 × 107 M⊙ (αCOGalactic) and 8.5 × 104 M⊙ and molecular and ionized outflow mass rates of ∼51 M⊙ yr−1 (αCOGalactic) and 0.14 M⊙ yr−1, respectively. This means that the molecular phase dominates the outflow mass and outflow mass rate, while the kinetic power and momentum of the outflow are similar in both phases. However, the wind momentum loads (Ṗout/ṖAGN) for the molecular and ionized outflow phases are ∼27−5 (αCOGalactic and αCOULIRGs) and < 1, which suggests that the molecular phase is not momentum conserving, but the ionized phase most certainly is. The molecular gas content (Meast ∼ 1.5 × 107 M⊙; αCOGalactic) of the eastern spiral arm is approximately 50−70% of the content of the western one. We interpret this as destruction or clearing of the molecular gas produced by the AGN wind impacting in the eastern side of the host galaxy (negative feedback process). The increase in molecular phase momentum implies that part of the kinetic energy from the AGN wind is transmitted to the molecular outflow. This suggests that in Seyfert-like AGN such as NGC 5643, the radiative or quasar and the kinetic or radio AGN feedback modes coexist and may shape the host galaxies even at kiloparsec scales through both positive and (mild) negative feedback.

Feedback of molecular outflows from protostars in NGC 1333 revealed by Herschel and Spitzer spectro-imaging observations

Context. Far infrared cooling of excited gas around protostars has been predominantly studied in the context of pointed observations. Large-scale spectral maps of star forming regions enable the simultaneous, comparative study of the gas excitation around an ensemble of sources at a common frame of reference, therefore, providing direct insights in the multitude of physical processes involved. Aims. We employ extended spectral-line maps to decipher the excitation, the kinematical, and dynamical processes in NGC 1333 as revealed by a number of different molecular and atomic lines, aiming to set a reference for the applicability and limitations of different tracers in constraining particular physical processes. Methods. We reconstructed line maps for H2, CO, H2O, and [C I] using data obtained with the Spitzer infrared spectrograph and the Herschel HIFI and SPIRE instruments. We compared the morphological features revealed in the maps and derive the gas excitation conditions for regions of interest employing local thermodynamic equilibrium (LTE) and non-LTE methods. We also calculated the kinematical and dynamical properties for each outflow tracer in a consistent manner for all observed outflows driven by protostars in NGC 1333. We finally measured the water abundance in outflows with respect to carbon monoxide and molecular hydrogen. Results. CO and H2 are highly excited around B-stars and, at lower, levels trace protostellar outflows. H2O emission is dominated by a moderately fast component associated with outflows. H2O also displays a weak, narrow-line component in the vicinity of B-stars associated to their ultraviolet (UV) field. This narrow component is also present in a few of outflows, indicating UV radiation generated in shocks. Intermediate J CO lines appear brightest at the locations traced by the narrow H2O component, indicating that beyond the dominating collisional processes, a secondary, radiative excitation component can also be active. The morphology, kinematics, excitation, and abundance variations of water are consistent with its excitation and partial dissociation in shocks. Water abundance ranges between 5 × 10−7 and ~10−5, with the lower values being more representative. Water is brightest and most abundant around IRAS 4A, which is consistent with the latter hosting a hot corino source. [C I] traces dense and warm gas in the envelopes surrounding protostars. Outflow mass flux is highest for CO and decreases by one and two orders of magnitude for H2 and H2O, respectively. Conclusions. Large-scale spectral line maps can provide unique insights into the excitation of gas in star-forming regions. A comparative analysis of line excitation and morphologies at different locations allows us to decipher the dominant excitation conditions in each region in addition to isolating exceptional cases.

Regression with Gaussian Mixture ModelsApplied to Track Fitting

This note describes the application of Gaussian mixture regression to track fitting with a Gaussian mixture model of the position errors. The mixture model is assumed to have two components with identical component means. Under the premise that the association of each measurement to a specific mixture component is known, the Gaussian mixture regression is shown to have consistently better resolution than weighted linear regression with equivalent homoskedastic errors. The improvement that can be achieved is systematically investigated over a wide range of mixture distributions. The results confirm that with constant homoskedastic variance the gain is larger for larger mixture weight of the narrow component and for smaller ratio of the width of the narrow component and the width of the wide component.

Structure of accretion flows in the nova-like cataclysmic variable RW Tri

ABSTRACT We obtained photometric observations of the nova-like (NL) cataclysmic variable RW Tri and gathered all available AAVSO and other data from the literature. We determined the system parameters and found their uncertainties using the code developed by us to model the light curves of binary systems. New time-resolved optical spectroscopic observations of RW Tri were also obtained to study the properties of emission features produced by the system. The usual interpretation of the single-peaked emission lines in NL systems is related to the bi-conical wind from the accretion disc’s inner part. However, we found that the Hα emission profile is comprised of two components with different widths. We argue that the narrow component originates from the irradiated surface of the secondary, while the broader component’s source is an extended, low-velocity region in the outskirts of the accretion disc, located opposite to the collision point of the accretion stream and the disc. It appears to be a common feature for long-period NL systems – a point we discuss.

Study of the variable broadband emission of Markarian 501 during the most extreme Swift X-ray activity

Context. Markarian 501 (Mrk 501) is a very high-energy (VHE) gamma-ray blazar located at z = 0.034, which is regularly monitored by a wide range of multi-wavelength instruments, from radio to VHE gamma rays. During a period of almost two weeks in July 2014, the highest X-ray activity of Mrk 501 was observed in ∼14 years of operation of the Neil Gehrels Swift Gamma-ray Burst Observatory. Aims. We characterize the broadband variability of Mrk 501 from radio to VHE gamma rays during the most extreme X-ray activity measured in the last 14 years, and evaluate whether it can be interpreted within theoretical scenarios widely used to explain the broadband emission from blazars. Methods. The emission of Mrk 501 was measured at radio with Metsähovi, at optical–UV with KVA and Swift/UVOT, at X-ray with Swift/XRT and Swift/BAT, at gamma ray with Fermi-LAT, and at VHE gamma rays with the FACT and MAGIC telescopes. The multi-band variability and correlations were quantified, and the broadband spectral energy distributions (SEDs) were compared with predictions from theoretical models. Results. The VHE emission of Mrk 501 was found to be elevated during the X-ray outburst, with a gamma-ray flux above 0.15 TeV varying from ∼0.5 to ∼2 times the Crab nebula flux. The X-ray and VHE emission both varied on timescales of 1 day and were found to be correlated. We measured a general increase in the fractional variability with energy, with the VHE variability being twice as large as the X-ray variability. The temporal evolution of the most prominent and variable segments of the SED, characterized on a day-by-day basis from 2014 July 16 to 2014 July 31, is described with a one-zone synchrotron self-Compton model with variations in the break energy of the electron energy distribution (EED), and with some adjustments in the magnetic field strength and spectral shape of the EED. These results suggest that the main flux variations during this extreme X-ray outburst are produced by the acceleration and the cooling of the high-energy electrons. A narrow feature at ∼3 TeV was observed in the VHE spectrum measured on 2014 July 19 (MJD 56857.98), which is the day with the highest X-ray flux (>0.3 keV) measured during the entire Swift mission. This feature is inconsistent with the classical analytic functions to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3σ. A fit with a log-parabola plus a narrow component is preferred over the fit with a single log-parabola at more than 4σ, and a dedicated Monte Carlo simulation estimated the significance of this extra component to be larger than 3σ. Under the assumption that this VHE spectral feature is real, we show that it can be reproduced with three distinct theoretical scenarios: (a) a pileup in the EED due to stochastic acceleration; (b) a structured jet with two-SSC emitting regions, with one region dominated by an extremely narrow EED; and (c) an emission from an IC pair cascade induced by electrons accelerated in a magnetospheric vacuum gap, in addition to the SSC emission from a more conventional region along the jet of Mrk 501.

Chemodynamics of green pea galaxies – I. Outflows and turbulence driving the escape of ionizing photons and chemical enrichment

ABSTRACT We investigate the ionized gas kinematics, physical properties, and chemical abundances of Sloan Digital Sky Survey J142947, a Green Pea galaxy at redshift z∼ 0.17 with strong, double-peak Ly α emission and indirect evidence of Lyman continuum (LyC) leakage. Using high-dispersion spectroscopy, we perform a multicomponent analysis of emission-line profiles. Our model consistently fits all lines as a narrow component with intrinsic velocity dispersion σ ∼ 40 km s−1, and two broader blue-shifted components with σ ∼ 90 and ∼ 250 km s−1. We find electron densities and temperatures, ionization conditions, and direct O/H and N/O abundances for each component. A highly ionized, metal-poor, young and compact starburst dominates narrow emission, showing evidence of hard radiation fields and elevated N/O. The blue-shifted broader components are consistent with highly turbulent, possibly clumpy ionized gas at the base of a strong photoionized outflow, which accounts for ≳50 per cent of the integrated emission-line fluxes. The outflow is dense and metal-enriched compared to the H ii regions, with expansion velocities larger than those obtained from UV interstellar absorption lines under standard assumptions. Some of these metals may be able to escape, with outflows loading factors comparable to those found in high-z galaxies of similar SFR/Area. Our findings depict a two-stage starburst picture; hard radiation fields from young star clusters illuminate a turbulent and clumpy ISM that has been eroded by SNe feedback. Whilst UV data suggest an extended Ly α halo with high average H i column density, LyC photons could only escape from SDSS J142947 through low H i density channels or filaments in the ISM approaching density-bounded conditions, traced by outflowing gas.

NGC 7469 as seen by MEGARA: new results from high-resolution IFU spectroscopy

ABSTRACT We present our analysis of high-resolution (R ∼ 20 000) GTC/MEGARA integral-field unit spectroscopic observations, obtained during the commissioning run, in the inner region (12.5 arcsec × 11.3 arcsec) of the active galaxy NGC 7469, at spatial scales of 0.62 arcsec. We explore the kinematics, dynamics, ionization mechanisms, and oxygen abundances of the ionized gas, by modelling the H α-[N ii] emission lines at high signal-to-noise (&gt; 15) with multiple Gaussian components. MEGARA observations reveal, for the first time for NGC 7469, the presence of a very thin (20 pc) ionized gas disc supported by rotation (V/σ = 4.3), embedded in a thicker (222 pc), dynamically hotter (V/σ = 1.3) one. These discs nearly corotate with similar peak-to-peak velocities (163 versus 137 km s−1), but with different average velocity dispersion (38 ± 1 versus 108 ± 4 km s−1). The kinematics of both discs could be possibly perturbed by star-forming regions. We interpret the morphology and the kinematics of a third (broader) component (σ &gt; 250 km s−1) as suggestive of the presence of non-rotational turbulent motions possibly associated either to an outflow or to the lense. For the narrow component, the [N ii]/H α ratios point to the star-formation as the dominant mechanism of ionization, being consistent with ionization from shocks in the case of the intermediate component. All components have roughly solar metallicity. In the nuclear region of NGC 7469, at r ≤ 1.85 arcsec, a very broad (FWHM = 2590 km s−1) H α component is contributing (41 per cent) to the global H α-[N ii] profile, being originated in the (unresolved) broad line region of the Seyfert 1.5 nucleus of NGC 7469.

Unveiling kinematic structure in the starburst heart of NGC 253

ABSTRACT We observed the Brackett α emission line (4.05 μm) within the nuclear starburst of NGC 253 to measure the kinematics of ionized gas, and distinguish motions driven by star formation feedback from gravitational motions induced by the central mass structure. Using NIRSPEC on Keck II, we obtained 30 spectra through a $0^{\prime \prime }_{.}5$ slit stepped across the central ∼5 arcsec × 25 arcsec (85 × 425 pc) region to produce a spectral cube. The Br α emission resolves into four nuclear sources: S1 at the infrared core (IRC), N1 at the radio core, and the fainter sources N2 and N3 in the northeast. The line profile is characterized by a primary component with Δvprimary ∼90–130 $\rm km\, s^{-1}$ (full width at half-maximum) on top of a broad blue 2wing with Δvbroad ∼300–350 $\rm km\, s^{-1}$, and an additional redshifted narrow component in the west. The velocity field generated from our cube reveals several distinct patterns. A mean NE–SW velocity gradient of +10 $\rm km\, s^{-1}$ arcsec−1 along the major axis traces the solid-body rotation curve of the nuclear disc. At the radio core, isovelocity contours become S-shaped, indicating the presence of secondary nuclear bar of total extent ∼5 arcsec (90 pc). The symmetry of the bar places the galactic centre, and potential supermassive black hole, near the radio peak rather than the IRC. A third kinematic substructure is formed by blueshifted gas near the IRC. This feature likely traces a ∼100–250 $\rm km\, s^{-1}$ starburst-driven outflow, potentially linking the IRC to the galactic wind observed on kpc scales.

BAT AGN Spectroscopic Survey – XIX. Type 1 versus type 2 AGN dichotomy from the point of view of ionized outflows

ABSTRACT We present a detailed study of ionized outflows in a large sample of ∼650 hard X-ray-detected active galactic neuclei (AGNs). Using optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS), we are able to reveal the faint wings of the [O iii] emission lines associated with outflows covering, for the first time, an unexplored range of low AGN bolometric luminosity at low redshift (z ∼0.05). We test if and how the incidence and velocity of ionized outflow is related to AGN physical parameters: black hole mass ($\rm \mathit{ M}_{BH}$), gas column density ($\rm \mathit{ N}_{H}$), Eddington ratio ($\rm \lambda _{Edd}$), [O iii], X-ray, and bolometric luminosities. We find a higher occurrence of ionized outflows in type 1.9 (55 per cent) and type 1 AGNs (46 per cent) with respect to type 2 AGNs (24 per cent). While outflows in type 2 AGNs are evenly balanced between blue and red velocity offsets with respect to the [O iii] narrow component, they are almost exclusively blueshifted in type 1 and type 1.9 AGNs. We observe a significant dependence between the outflow occurrence and accretion rate, which becomes relevant at high Eddington ratios [log($\rm \lambda _{Edd}$) ≳ −1.7]. We interpret such behaviour in the framework of covering factor-Eddington ratio dependence. We do not find strong trends of the outflow maximum velocity with AGN physical parameters, as an increase with bolometric luminosity can be only identified when including samples of AGNs at high luminosity and high redshift taken from literature.