The spatially resolved gas and dust connection in neutral inflows and outflows in nearby AGN

ABSTRACT Dusty, neutral outflows and inflows are a common feature of nearby star-forming galaxies. We characterize these flows in eight galaxies – mostly active galactic nuclei (AGN) – selected for their widespread Na i D signatures from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). This survey employs deep, wide field-of-view (FOV) integral field spectroscopy at moderate spectral resolution (R = 7000 at Na i D). We significantly expand the sample of sightlines in external galaxies in which the spatially resolved relationship has been studied between cool, neutral gas properties – N(Na i), Weq(Na i D) – and dust – E(B − V) from both stars and gas. Our sample shows strong, significant correlations of total Weq with E(B − V)⋆ and g − i colour within individual galaxies; correlations with E(B − V)gas are present but weaker. Regressions yield slope variations from galaxy to galaxy and intrinsic scatter ∼1 Å. The sample occupies regions in the space of N(Na i) and $W_\mathrm{eq}^\mathrm{abs}$ versus E(B − V)gas that are consistent with extrapolations from other studies to higher colour excess [E(B − V)gas ∼ 1]. For perhaps the first time in external galaxies, we detect inverse P Cygni profiles in the Na i D line, presumably due to inflowing gas. Via Doppler-shifted Na i D absorption and emission lines, we find ubiquitous flows that differ from stellar rotation by $\gtrsim$100 km s−1 or have $|v_{\mathrm{ abs}} - v_{\mathrm{ em}}|\gtrsim 100$ km s−1. Inflows and outflows extend towards the edge of the detected stellar disc/FOV, together subtend 10–40 per cent of the projected disc, and have similar mean N(Na i) and Weq(Na i D). Outflows are consistent with minor axis or jet-driven flows, while inflows tend towards the projected major axis. The inflows may result from non-axisymmetric potentials, tidal motions, or halo infall.

The kinematics of young and old stellar populations in nuclear rings of MUSE TIMER galaxies

Context. Studying the stellar kinematics of galaxies is a key tool in the reconstruction of their evolution. However, the current measurements of the stellar kinematics are complicated by several factors, including dust extinction and the presence of multiple stellar populations. Aims. We use integral field spectroscopic data of four galaxies from the Time Inference with MUSE in Extragalactic Rings (TIMER) survey to explore and compare the kinematics measured in different spectral regions that are sensitive to distinct stellar populations. Methods. We derive the line-of-sight velocity and velocity dispersion of both a young (≲2 Gyr) and an old stellar population from the spectral regions around the Hβ line and the Ca II Triplet. In addition, we determine colour excess, mean age, and metallicity. Results. We report a correlation of the colour excess with the difference in the kinematic parameters of the Hβ line and the Ca II Triplet range, which are dominated by young and old stellar populations, respectively. Young stellar populations, located primarily in nuclear rings, have higher velocity dispersions than old ones. These differences in the rings are typically ∼10 km s−1 in velocity dispersion but can have a mean value as high as ∼24 km s−1 in the most extreme case. Trends with age exist in the nuclear rings but are less significant than those with dust extinction. We report different degrees of correlation for these trends among the galaxies in the sample, which are related to the size of the Voronoi bins in their rings. No clear trends for the line-of-sight velocity differences are observed. The absence of these trends can be explained as a consequence of the Hβ line masking process during the kinematic extraction, as confirmed by dedicated simulations. Conclusions. Our study demonstrates that kinematic differences caused by different stellar populations can be identified in the central regions of nearby galaxies, even from intermediate resolution spectroscopy. This opens the door to future detailed chemo-kinematic studies of galaxies, but also serves as a warning against deriving kinematics from full-spectrum fitting across very wide wavelength ranges when intense star formation is taking place.

A revision of the vdB 130 cluster stellar content based on Gaia DR2 data: interstellar extinction toward the Cyg OB1 supershell

ABSTRACT Two star-forming regions are studied: the young embedded open cluster vdB 130 and the protocluster neighbourhood observed in the head and tail of the cometary molecular cloud located in the wall of the expanding supershell surrounding the Cyg OB1 association. The Gaia DR2 catalogue is employed to verify the stellar composition of the vdB 130 cluster whose members were earlier selected using the UCAC4 catalogue. The new sample of vdB 130 members contains 68 stars with close proper motions (within 1 mas yr−1) and close trigonometric parallaxes (ranging from 0.50–0.70 mas). The relative parallax error is shown to increase with distance to objects and depend on their magnitude. At a distance of 1.5–2 kpc it is of about 3–7 per cent and 20–30 per cent for bright and faint stars, respectively. The cluster is not older than ∼10 Myr. New spectroscopic and photometric observations carried out on Russian telescopes are combined with Gaia DR2 to search for optical components in the protocluster region – a new starburst. An analysis of 20 stars in the vicinity of the protocluster revealed no concentration of either proper motions or parallaxes. According to spectroscopic, photometric and trigonometric estimates, the distances to these stars range from 0.4–2.5 kpc, and colour excess is shown to increase with a distance D (kpc) in accordance with the law E(B − V) ≃ 0.6 × D mag.

The brown dwarf population in the star-forming region NGC 2264

ABSTRACT The brown dwarf population in the canonical star-forming region NGC 2264 is so far poorly explored. We present a deep, multiwavelength, multiepoch survey of the star-forming cluster NGC 2264, aimed to identify young brown dwarf candidates in this region. Using criteria including optical/near-infrared (IR) colours, variability, Spitzer mid-IR colour excess, extinction, and Gaia parallax and proper motion (in order of relevance), we select 902 faint red sources with indicators of youth. Within this sample, we identify 429 brown dwarf candidates based on their IR colours. The brown dwarf candidates are estimated to span a mass range from 0.01 to 0.08 M⊙. We find rotation periods for 44 sources, 15 of which are brown dwarf candidates, ranging from 3.6 h to 6.5 d. A subset of 38 brown dwarf candidates show high-level irregular variability indicative of ongoing disc accretion, similar to the behaviour of young stars.

Mapping local interstellar medium with diffuse interstellar bands

ABSTRACT With the use of the data from archives, we studied the correlations between the equivalent widths of four diffuse interstellar bands (4430, 5780, 5797, 6284 $\mathring{\rm A}$) and properties of the target stars (colour excess values, distances, and Galactic coordinates). Many different plots of the diffuse interstellar bands and their maps were produced and further analysed. There appears to be a structure in the plot of equivalent widths of 5780 $\mathring{\rm A}$ DIB (and 6284 $\mathring{\rm A}$ DIB) against the Galactic x-coordinate. The structure is well defined below ∼ 150 m$\mathring{\rm A}$ and within |x| < 250 pc, peaking around x = 170 pc. We argue that the origin of this structure is not a statistical fluctuation. Splitting the data in the Galactic longitude into several subregions improve or lower the well-known linear relation between the equivalent widths and the colour excess, which was expected. However, some of the lines of sight display drastically different behaviour. The region within 150° < l < 200° shows scatter in the correlation plots with the colour excess for all of the four bands with correlation coefficients R < 0.58. We suspect that the variation of physical conditions in the nearby molecular clouds could be responsible. Finally, the area 250° < l < 300° displays (from the statistical point of view) significantly lower values of equivalent widths than the other regions – this tells us that there is either a significant underabundance of carriers (when compared with the other regions) or that this has to be a result of an observational bias.

A survey of extended matter around chromospherically active binary systems

We present an analysis of colour excess (CE) observations for 13 chromospherically active binary systems, together with 27 inactive reference stars of similar spectral types and luminosity classes of the components of these 13 binaries. We used the observations which were made by Johnson-Cousins ${BVR}_{c}\mathrm{I}_{c}$ , 2MASS, and WISE photometric systems. Our new photometric ${BVR}_{c}\mathrm{I}_{c}$ observations were obtained by means of 1 m telescope at TÜBİTAK National Observatory and 40 cm telescope at Ankara University Kreiken Observatory. To check the existence of extended matter around an active binary component(s) of these 13 binary systems, we examined the CE values at around primary/secondary minima and outside eclipses. The comparison of these CEs, obtained relative to those of reference stars of the same ${(B-V)_\circ}$ colours, especially during primary minima with those of secondary minima and outside eclipses, showed that these systems have greater excess radiation in primary minima than in both secondary minima and outside eclipses. We observed that the colour excesses, in general, most likely arise from the extended matter around the cooler component of a binary system. The comparison of CE values also showed that the extended matter of some of these systems was most likely covered or affected both of their components. Since no observational data were obtained during primary minimum of RW UMa, by excluding this binary system, an examination of the locations of cool and active components of the remaining 12 systems of this study on Hertzsprung-Russell diagram, together with corresponding evolutionary tracks, showed that most of the active binary systems have an extended matter not only caused from stellar activity but also more likely caused from evolutionary processes.

Following the crumbs: statistical effects of ram pressure in galaxies

ABSTRACT We analyse the presence of dust around galaxy group members through the reddening of background quasars. By taking into account quasar colour and their dependence on redshift and angular position, we derive mean quasar colours excess in projected regions around member galaxies and infer the associated dust mass. For disc-like galaxies perpendicular to the plane of the sky, and at groupcentric distances of the order of the virial radius, thus likely to reside in the infall regions of groups, we find systematic colour excess values e ∼ 0.009 ± 0.004 for g − r colour. Under the hypothesis of Milky Way dust properties, we derive dust masses of $5.8 \pm 2.5 \times 10^8 \, \mathrm{M}_{\odot }\, h^{-1}$, implying that a large fraction of dust is being stripped from galaxies in their path to groups. We also studied the photometry of member galaxies to derive a colour asymmetry relative to the group centre direction from a given galaxy. We conclude that the regions of galaxies facing the centre are bluer, consistent with the effects of gas compression and star formation. We also combine these two procedures finding that galaxies with a small colour asymmetry show the largest amounts of dust towards the external regions compared to a control sample. We conclude that dust removal is very efficient in galaxies on infall. The fact that galaxies redder towards groups centres are associated with the strongest reddening of background quasars suggest that gas removal induced by ram pressure stripping plays a key role in galaxy evolution and dust content.

A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys

An improved high-resolution and deep $A_{K_{s}}$ foreground dust extinction map is presented for the Galactic disc area within 295° ≲ l ≲ 350°, −1.0° ≲ b ≲ +1.0°. At some longitudes the map reaches up to |b| ∼ 2.25°, for a total of ∼148 deg2. The map was constructed via the Rayleigh–Jeans colour excess (RJCE) technique based on deep near-infrared (NIR) and mid-infrared (MIR) photometry. The new extinction map features a maximum bin size of 1 arcmin, and relies on NIR observations from the Two Micron All-Sky Survey (2MASS) and new data from ESO’s Vista Variables in the Vía Láctea (VVV) survey, in concert with MIR observations from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. The VVV photometry penetrates ∼4 mag fainter than 2MASS, and provides enhanced sampling of the underlying stellar populations in this heavily obscured region. Consequently, the new results supersede existing RJCE maps tied solely to brighter photometry, revealing a systematic underestimation of extinction in prior work that was based on shallower data. The new high-resolution and large-scale extinction map presented here is readily available to the community through a web query interface.

VISION - Vienna Survey in Orion

We have investigated the shape of the extinction curve in the infrared up to ~25μm for the Orion A star-forming complex. The basis of this work is near-infrared data acquired with the Visual and Infrared Survey Telescope for Astronomy, in combination with Pan-STARRS and mid-infrared Spitzer photometry. We obtain colour excess ratios for eight passbands by fitting a series of colour-colour diagrams. The fits are performed using Markov chain Monte Carlo methods, together with a linear model under a Bayesian formalism. The resulting colour excess ratios are directly interpreted as a measure of the extinction law. We show that the Orion A molecular cloud is characterized by flat mid-infrared extinction, similar to many other recently studied sightlines. Moreover, we find statistically significant evidence that the extinction law from ~1μm to at least ~6μm varies across the cloud. In particular, we find a gradient along galactic longitude, where regions near the Orion Nebula Cluster show a different extinction law compared to L1641 and L1647, the low-mass star-forming sites in the cloud complex. These variations are of the order of only 3% and are most likely caused by the influence of the massive stars on their surrounding medium. While the observed general trends in our measurements are in agreement with model predictions, both well-established and new dust grain models are not able to fully reproduce our infrared extinction curve. We also present a new extinction map featuring a resolution of 1′ and revisit the correlation between extinction and dust optical depth. This analysis shows that cloud substructure, which is not sampled by background sources, affects the conversion factor between these two measures. In conclusion, we argue that specific characteristics of the infrared extinction law are still not well understood, but Orion A can serve as an unbiased template for future studies.