Archival Hubble Space Telescope Research Articles

Single metal-poor ultra compact dwarf galaxy at one kiloparsec distance from the low-mass elliptical galaxy FCC 47

Context. Photometric surveys of galaxy clusters have revealed a large number of ultra compact dwarfs (UCDs) around predominantly massive elliptical galaxies. Their origin is still debated as some UCDs are considered to be the remnant nuclei of stripped dwarf galaxies while others seem to mark the high-mass end of the star cluster population.Aims. We aim to characterize the properties of a UCD found at very close projected distance (rwproj= 1.1 kpc) from the centre of the low-mass (M ∼ 1010 M⊙) early-type galaxy FCC 47. This is a serendipitous discovery from MUSE adaptive optics science verification data. We explore the potential origin of this UCD as either a massive cluster or the remnant nucleus of a dissolved galaxy.Methods. We used archivalHubbleSpace Telescope data to study the photometric and structural properties of FCC 47-UCD1. In the MUSE data, the UCD is unresolved, but we used its spectrum to determine the radial velocity and metallicity.Results. The surface brightness of FCC 47-UCD1 is best described by a single King profile with low concentrationC = Rt/Rc ∼ 10 and large effective radius (reff = 24 pc). Its integrated magnitude and blue colour (Mg = −10.55 mag, (g − z) = 1.46 mag) combined with a metallicity of [M/H] = −1.12 ± 0.10 dex and an age > 8 Gyr obtained from the full fitting of the MUSE spectrum suggests a stellar population mass ofM* = 4.87 × 106 M⊙. The low S/N of the MUSE spectrum prevents detailed stellar population analysis. Due to the limited spectral resolution of MUSE, we can only give an upper limit on the velocity dispersion (σ < 17 km s−1), and consequently on its dynamical mass (Mdyn < 1.3 × 107 M⊙).Conclusions. The origin of the UCD cannot be constrained with certainty. The low metallicity, old age, and magnitude are consistent with a star cluster origin, whereas the extended size is consistent with an origin as the stripped nucleus of a dwarf galaxy with a initial stellar mass of a few 108 M⊙.

The Type II-plateau Supernova 2017eaw in NGC 6946 and Its Red Supergiant Progenitor

Abstract We present extensive optical photometric and spectroscopic observations, from 4 to 482 days after explosion, of the Type II-plateau (II-P) supernova (SN) 2017eaw in NGC 6946. SN 2017eaw is a normal SN II-P intermediate in properties between, for example, SN 1999em and SN 2012aw and the more luminous SN 2004et, also in NGC 6946. We have determined that the extinction to SN 2017eaw is primarily due to the Galactic foreground and that the SN site metallicity is likely subsolar. We have also independently confirmed a tip-of-the-red-giant-branch (TRGB) distance to NGC 6946 of 7.73 ± 0.78 Mpc. The distances to the SN that we have also estimated via both the standardized candle method and expanding photosphere method corroborate the TRGB distance. We confirm the SN progenitor identity in pre-explosion archival Hubble Space Telescope (HST) and Spitzer Space Telescope images, via imaging of the SN through our HST Target of Opportunity program. Detailed modeling of the progenitor’s spectral energy distribution indicates that the star was a dusty, luminous red supergiant consistent with an initial mass of ∼15 M ⊙.

AT 2017fvz: a nova in the dwarf irregular galaxy NGC 6822

ABSTRACT A transient in the Local Group dwarf irregular galaxy NGC 6822 (Barnard’s Galaxy) was discovered on 2017 August 2 and is only the second classical nova discovered in that galaxy. We conducted optical, near-ultraviolet, and X-ray follow-up observations of the eruption, the results of which we present here. This ‘very fast’ nova had a peak V-band magnitude in the range −7.41 > MV > −8.33 mag, with decline times of t2,V = 8.1 ± 0.2 d and t3,V = 15.2 ± 0.3 d. The early- and late-time spectra are consistent with an Fe ii spectral class. The H α emission line initially has a full width at half-maximum intensity of ∼2400 km s−1 – a moderately fast ejecta velocity for the class. The H α line then narrows monotonically to ∼1800 km s−1 by 70 d post-eruption. The lack of a pre-eruption coincident source in archival Hubble Space Telescope imaging implies that the donor is a main-sequence, or possibly subgiant, star. The relatively low-peak luminosity and rapid decline hint that AT 2017fvz may be a ‘faint and fast’ nova.

Optical Counterparts of ULXs and Their Host Environments in NGC 4490/4485

Abstract We report the identification of the possible optical counterparts of five out of seven ultraluminous X-ray sources (ULXs) in the galaxy pair NGC 4490/4485. Using archival Hubble Space Telescope (HST) imaging data, we identified a single optical candidate for two ULXs (X-4 and X-7) and multiple optical candidates for the other three (X-2, X-3, and X-6) within ∼0.″2 error radius at the 90% confidence level. Of the two remaining ULXs, X-1 has no HST imaging data, and photometry could not be performed due to the position of X-5 in NGC 4490. Absolute magnitudes (M V ) of the optical candidates lie between −5.7 and −3.8. Color–magnitude diagrams have been used to investigate the properties of the counterparts and their environments. The locations of the counterparts of X-2, X-4, and X-6 suggest possible association with a nearby group of stars, while the others have no association with a star cluster or group of stars. For comparison purposes, we analyzed three previously unused archival XMM-Newton observations. The long-term X-ray light curves of the sources (except transient X-7) show variability by a factor of three on a timescale of more than a decade. The use of a disk blackbody model for the mass of the compact objects indicates that these objects most likely have masses in the range 10–15 M ☉.

The mass and density of the dwarf planet (225088) 2007 OR10

The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e ≈ 0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused by the Kozai mechanism. Dynamical considerations also suggest that the moon is small, Deff < 100 km. Based on the newly determined system mass of 1.75 ·1021 kg, 2007 OR10 is the fifth most massive dwarf planet after Eris, Pluto, Haumea and Makemake. The newly determined orbit has also been considered as an additional option in our radiometric analysis, provided that the moon orbits in the equatorial plane of the primary. Assuming a spherical shape for the primary this approach provides a size of 1230 ± 50 km, with a slight dependence on the satellite orbit orientation and primary rotation rate chosen, and a bulk density of 1.75 ± 0.07 g cm−3 for the primary. A previous size estimate that assumed an equator-on configuration (1535−225+75 km) would provide a density of 0.92−0.14+0.46 g cm−3, unexpectedly low for a 1000 km-sized dwarf planet.

Multiple Spiral Arms in the Disk around Intermediate-mass Binary HD 34700A

We present the first images of the transition disk around the close binary system HD 34700A in polarized scattered light using the Gemini Planet Imager instrument on Gemini South. The J and H band images reveal multiple spiral-arm structures outside a large (R = 0.49" = 175 au) cavity along with a bluish spiral structure inside the cavity. The cavity wall shows a strong discontinuity and we clearly see significant non-azimuthal polarization Uphi consistent with multiple scattering within a disk at an inferred inclination ~42deg. Radiative transfer modeling along with a new Gaia distance suggest HD 37400A is a young (~5 Myr) system consisting of two intermediate-mass (~2Msun) stars surrounded by a transitional disk and not a solar-mass binary with a debris disk as previously classified. Conventional assumptions of the dust-to-gas ratio would rule out a gravitational instability origin to the spirals while hydrodynamical models using the known external companion or a hypothetical massive protoplanet in the cavity both have trouble reproducing the relatively large spiral arm pitch angles (~30deg) without fine tuning of gas temperature. We explore the possibility that material surrounding a massive protoplanet could explain the rim discontinuity after also considering effects of shadowing by an inner disk. Analysis of archival Hubble Space Telescope data suggests the disk is rotating counterclockwise as expected from the spiral arm structure and revealed a new low-mass companion at 6.45" separation. We include an appendix which sets out clear definitions of Q, U, Qphi, Uphi, correcting some confusion and errors in the literature.

Searching for the Donor Stars of ULX Pulsars

Abstract We report on our search for the optical counterparts of two ultraluminous X-ray pulsars with known orbital periods, M82 X-2 and NGC 5907 X-1, in new and archival Hubble Space Telescope observations, in an effort to characterize the donor stars in these systems. We detect five near-infrared sources consistent with the position of M82 X-2 that are too bright to be single stars. We also detect seven sources in the WFC3/UVIS F336W image whose photometry matches that of 10–15 M ⊙ stars turning off the main sequence. Such stars have densities consistent with the properties of the donor star of M82 X-2 as inferred from X-ray timing analysis, although it is also possible that the donor is a lower-mass star below our detection limit or that there is a significant contribution from the accretion disk to the optical emission. We detect three candidate counterparts to NGC 5907 X-1 in the near-infrared. All of these are too bright to be the donor star of the ultraluminous X-ray source (ULX), which, based on its orbital period, is a red giant. The high background at the location of NGC 5907 X-1 precludes us from detecting this expected donor star. The recently discovered NGC 5907 ULX-2 also falls within the field of view of the near-infrared imaging; we detect four sources in the error circle, with photometry that matches asymptotic giant branch stars. The star suggested to be the counterpart of NGC 5907 ULX-2 by Pintore et al. falls outside our 2σ error circle.

New luminous blue variable candidates in NGC 4736

ABSTRACT We have found three new luminous blue variable (LBV) candidates in the star-forming galaxy NGC 4736. They show typical well-known LBV spectra, broad and strong hydrogen lines, He i lines, many Fe ii lines, and forbidden [Fe ii] and [Fe iii]. Using archival Hubble Space Telescope and ground-based telescope data, we have estimated the bolometric magnitudes of these objects from −8.4 to −11.5, temperatures, and reddening. Source NGC 4736_1 (M$v$ = −10.2 ± 0.1 mag) demonstrated variability between 2005 and 2018 as ΔV ≈ 1.1 mag and ΔB ≈ 0.82 mag; the object belongs to LBV stars. NGC 4736_2 (M$v$ &amp;lt; −8.6 mag) shows P Cyg profiles and its spectrum has changed from 2015 to 2018. The brightness variability of NGC 4736_2 is ΔV ≈ 0.5 mag and ΔB ≈ 0.4 mag. In NGC 4736_3 (M$v$ = −8.2 ± 0.2 mag), we found strong nebular lines, broad wings of hydrogen; the brightness variation is only ≈0.2 mag. Therefore, the last two objects may reside to LBV candidates.

Reanalysis of the Gaia Data Release 2 photometric sensitivity curves using HST/STIS spectrophotometry

Context. The second data release (DR2) from the European Space Agency mission Gaia took place on April 2018. DR2 included photometry for more than 1.3 × 109 sources in the three bands G, GBP, and GRP. Even though the Gaia DR2 photometry is very precise, there are currently three alternative definitions of the sensitivity curves that show significative differences. Aims. The aim of this paper is to improve the quality of the input calibration data to produce new compatible definitions of the G, GBP, and GRP bands and to identify the reasons for the discrepancies between previous definitions. Methods. We have searched the Hubble Space Telescope (HST) archive for Space Telescope Imaging Spectrograph (STIS) spectra with G430L+G750L data obtained with wide apertures and combined them with the CALSPEC library to produce a high quality spectral energy distribution (SED) library of 122 stars with a broad range of colors, including three very red stars. This library defines new sensitivity curves for G, GBP, and GRP using a functional analytical formalism. Results. The new sensitivity curves are significantly better than the two previous attempts we use as a reference, REV (Evans et al. 2018, A&amp;A, 616, A4) and WEI (Weiler 2018, A&amp;A, 616, A17). For G we confirm the existence of a systematic bias in magnitude and correct a color term present in REV. For GBP we confirm the need to define two magnitude ranges with different sensitivity curves and measure the cut between them at Gphot = 10.87 mag with a significant increase in precision. The new curves also fit the data better than either REV or WEI. For GRP, our new sensitivity curve fits the STIS spectra better and the differences with previous attempts reside in a systematic effect between ground-based and HST spectral libraries. Additional evidence from color–color diagrams indicate that the new sensitivity curve is more accurate. Nevertheless, there is still room for improvement in the accuracy of the sensitivity curves because of the current dearth of good-quality red calibrators: adding more to the sample should be a priority before Gaia data release 3 takes place.

Parameters and models of the jets from Sanduleak’s star in the LMC

Context. Angeloni and collaborators have discovered a bipolar jet extending out to ~6 pc from “Sanduleak’s star” in the Large Magellanic Cloud (LMC). This is the first angularly resolved stellar jet system that has been observed outside our Galaxy. Aims. In this paper we use archival Hubble Space Telescope (HST) images of this jet in order to estimate the flow parameters, and use them to explore two possible theoretical scenarios for modelling this bipolar outflow. Methods. We have computed axisymmetric gasdynamic simulations of a conical outflow with an opening angle that increases with time and of a cylindrical jet interacting with a stratified circumstellar structure. The results of these models are then compared with the observed morphology of the jets from Sanduleak’s star. Results. From the observations, we obtain Ṁj ≈ 1.2 × 10−5M⊙ yr−1 and Lm ≈ 1000 L⊙ for the mass loss rate and the mechanical luminosity (respectively) of each of the outflow lobes. We also obtain a (deprojected) flow velocity vj ≈ 1000 km s−1 and a dynamical time tdyn ≈ 7300 yr. From the simulations that we have computed (with these flow parameters), we find that both the “opening out conical wind” and the “jet+stratified environment” scenarios have characteristics that resemble the observed morphologies. A more complete model for the jets from Sanduleak’s star might incorporate some of the features of these two scenarios.

Massive star population of the Virgo Cluster galaxy NGC4535

We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We performed high precision point spread function fitting photometry of 24353 sources including 3762 candidate blue supergiants, 841 candidate yellow supergiants, and 370 candidate red supergiants. We estimated the ratio of blue to red supergiants as a decreasing function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) isochrones at solar metallicity, we defined the luminosity function and estimated the star formation history of the galaxy over the last 60 Myr. We conducted a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von-Neumann ratio. This analysis yielded 120 new variable candidates with absolute magnitudes ranging from MV = −4 to −11 mag. We used the MESA evolutionary tracks at solar metallicity to classify the variables based on their absolute magnitude and their position on the color-magnitude diagram. Among the new candidate variable sources are eight candidate variable red supergiants, three candidate variable yellow supergiants and one candidate luminous blue variable, which we suggest for follow-up observations.

Ruprecht 106: A Riddle, Wrapped in a Mystery, inside an Enigma∗

Abstract Galactic globular clusters (GCs) show overwhelming photometric and spectroscopic evidence for the existence of multiple stellar populations. The question of whether or not there exists a GC that represents a true “simple stellar population” remains open. Here we focus on Ruprecht 106 (R106), a halo GC with [Fe/H] = −1.5 and [α/Fe] ≃0. A previous spectroscopic study found no sign of the Na–O anticorrelation among nine of its brightest red giants, which led to the conclusion that R106 is a true simple stellar population GC. Here we present new Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) photometry of R106 that, when combined with archival HST images spanning a 6 year baseline, allows us to create proper-motion cleaned color–magnitude diagrams spanning the ultraviolet (F336W) to the near-infrared (F814W). These data allow us to construct the pseudo-color that is sensitive to the presence of light-element abundance spreads. We find no evidence of a split along the red giant branch (RGB) in the diagram but the width of the RGB ( ) is marginally broader than expected from artificial star tests ( ). The observed spread in is smaller than any other Galactic GC studied to date. Our results raise important questions about the role of formation environment and primordial chemical composition in the formation of multiple stellar populations in GCs.

Delayed Stellar Mass Assembly in the Low Surface Brightness Dwarf Galaxy KDG 215∗

Abstract We present H i spectral line and optical broadband images of the nearby low surface brightness dwarf galaxy KDG 215. The H i images, acquired with the Karl G. Jansky Very Large Array, reveal a dispersion-dominated interstellar medium with only weak signatures of coherent rotation. The H i gas reaches a peak mass surface density of 6 M ⊙ pc−2 at the location of the peak surface brightness in the optical and the ultraviolet. Although KDG 215 is gas-rich, the Hα non-detection implies a very low current massive star formation rate. In order to investigate the recent evolution of this system, we have derived the recent and lifetime star formation histories from archival Hubble Space Telescope images. The recent star formation history shows a peak star formation rate ∼1 Gyr ago, followed by a decreasing star formation rate to the present day quiescent state. The cumulative star formation history indicates that a significant fraction of the stellar mass assembly in KDG 215 has occurred within the last 1.25 Gyr. KDG 215 is one of only a few known galaxies that demonstrates such a delayed star formation history. While the ancient stellar population (predominantly red giants) is prominent, the look-back time by which 50% of the mass of all stars ever formed had been created is among the youngest of any known galaxy.

Using High-Mass X-ray binaries to probe massive binary evolution: The age distribution of High-Mass X-ray binaries in M33

AbstractHigh-mass X-ray binaries (HMXBs) provide an exciting window into the underlying processes of both binary as well as massive star evolution. Because HMXBs are systems containing a compact object accreting from a high-mass star at close orbital separations they are also likely progenitors of gamma-ray bursts and gravitational wave sources. We present classification and age measurements for HMXBs in M33 using a combination of deep Chandra X-ray imaging, and archival Hubble Space Telescope data. We constrain the ages of the HMXB candidates by fitting the color-magnitude diagrams of the surrounding stars, which yield the star formation histories of the surrounding region. Unlike the age distributions measured for HMXB populations in the Magellanic Clouds, the age distribution for the HMXB population in M33 contains a number of extremely young (&lt;5 Myr) sources. We discuss these results the context of the effect of host galaxy properties on the observed HMXB population.

The Distance to the Galaxy Coma P

Abstract If the extremely low surface-brightness galaxy Coma P lies at 5.5 ± 0.3 Mpc, as recently proposed, then it would have an extraordinarily deviant peculiar velocity of ∼900 km s−1 at a location where differential velocities between galaxies are low. We have accessed the images from the Hubble Space Telescope (HST) archives used to derive the literature distance from the magnitude of the tip of the red giant branch. Our analysis gives the distance to be 10.9 ± 1.0 Mpc. At this location the galaxy lies within the infall region of the Virgo Cluster, such that its still considerable peculiar velocity of ∼500 km s−1 is consistent with an established model. Coma P has an unusually pronounced asymptotic giant branch (AGB) relative to its red giant branch. The dominant stellar population is just a few Gyr old.

The Progenitor Age and Mass of the Black Hole Formation Candidate N6946-BH1

Abstract The failed supernova N6946-BH1 likely formed a black hole (BH); we age-date the surrounding population and infer an age and initial mass for the progenitor of this BH formation candidate. First, we use archival Hubble Space Telescope imaging to extract broadband photometry of the resolved stellar populations surrounding this event. Using this photometry, we fit stellar evolution models to the color–magnitude diagrams to measure the recent star formation history (SFH). Modeling the photometry requires an accurate distance; therefore, we measure the tip of the red giant branch and infer a distance modulus of 29.47 ± 0.079 to NGC 6946, or a metric distance of 7.83 ± 0.29 Mpc. To estimate the stellar population’s age, we convert the SFH and uncertainties into a probabilistic distribution for the progenitor’s age. The region in the immediate vicinity of N6946-BH1 exhibits the youngest and most vigorous star formation for several hundred pc. This suggests that the progenitor is not a runaway star. From these measurements, we infer an age for the BH progenitor of Myr. Assuming that the progenitor evolved effectively as a single star, this corresponds to an initial mass of M ⊙. Previous spectral energy distribution (SED) modeling of the progenitor suggests a mass of ∼27 M ⊙. Formally, the SED-derived mass falls within our narrowest 68% confidence interval; however, 91% of the probability distribution function we measure lies below that mass, putting some tension between the age and the direct-imaging results.

SN 2017ein and the Possible First Identification of a Type Ic Supernova Progenitor

Abstract We have identified a progenitor candidate in archival Hubble Space Telescope (HST) images for the Type Ic supernova (SN Ic) SN 2017ein in NGC 3938, pinpointing the candidate’s location via HST Target of Opportunity imaging of the SN itself. This would be the first identification of a stellar-like object as a progenitor candidate for any SN Ic to date. We also present observations of SN 2017ein during the first ∼49 days since explosion. We find that SN 2017ein most resembles the well-studied SN Ic SN 2007gr. We infer that SN 2017ein experienced a total visual extinction of A V ≈ 1.0–1.9 mag, predominantly because of dust within the host galaxy. Although the distance is not well known, if this object is the progenitor, it was likely of high initial mass, ∼47–48 M ⊙ if a single star, or ∼60–80 M ⊙ if in a binary system. However, we also find that the progenitor candidate could be a very blue and young compact cluster, further implying a very massive (&gt;65 M ⊙) progenitor. Furthermore, the actual progenitor might not be associated with the candidate at all and could be far less massive. From the immediate stellar environment, we find possible evidence for three different populations; if the SN progenitor was a member of the youngest population, this would be consistent with an initial mass of ∼57 M ⊙. After it has faded, the SN should be reobserved at high spatial resolution and sensitivity, to determine whether the candidate is indeed the progenitor.

Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84

Abstract We report an optical/UV jet and counterjet in M84, previously unreported in archival Hubble Space Telescope imaging. With archival VLA, ALMA, and Chandra imaging, we examine the first well-sampled spectral energy distribution of the inner jet of M84, where we find that multiple co-spatial spectral components are required. In particular, the ALMA data reveal that the radio spectrum of all four knots in the jet turns over at approximately 100 GHz, which requires a second component for the bright optical/UV emission. Further, the optical/UV has a soft spectrum and is inconsistent with the relatively flat X-ray spectrum, which indicates a third component at higher energies. Using archival VLA imaging, we have measured the proper motion of the innermost knots at 0.9 ± 0.6 and 1.1 ± 0.4c, which when combined with the low jet-to-counterjet flux ratio yields an orientation angle for the system of °. In the radio, we find high fractional polarization of the inner jet of up to 30% while in the optical no polarization is detected (&lt;8%). We investigate different scenarios for explaining the particular multicomponent spectral energy distribution (SED) of the knots. Inverse Compton models are ruled out due to the extreme departure from equipartition and the unrealistically high total jet power required. The multicomponent SED can be naturally explained within a leptohadronic scenario, but at the cost of very high power in relativistic protons. A two-component synchrotron model remains a viable explanation, but more theoretical work is needed to explain the origin and properties of the electron populations.

Chemically Dissected Rotation Curves of the Galactic Bulge from Main-sequence Proper Motions*

Abstract We report results from an exploratory study implementing a new probe of Galactic evolution using archival Hubble Space Telescope imaging observations. Precise proper motions are combined with photometric relative metallicity and temperature indices, to produce the proper-motion rotation curves of the Galactic bulge separately for metal-poor and metal-rich main-sequence samples. This provides a “pencil-beam” complement to large-scale wide-field surveys, which to date have focused on the more traditional bright giant branch tracers. We find strong evidence that the Galactic bulge rotation curves drawn from “metal-rich” and “metal-poor” samples are indeed discrepant. The “metal-rich” sample shows greater rotation amplitude and a steeper gradient against line-of-sight distance, as well as possibly a stronger central concentration along the line of sight. This may represent a new detection of differing orbital anisotropy between metal-rich and metal-poor bulge objects. We also investigate selection effects that would be implied for the longitudinal proper-motion cut often used to isolate a “pure-bulge” sample. Extensive investigation of synthetic stellar populations suggests that instrumental and observational artifacts are unlikely to account for the observed rotation curve differences. Thus, proper-motion-based rotation curves can be used to probe chemodynamical correlations for main-sequence tracer stars, which are orders of magnitude more numerous in the Galactic bulge than the bright giant branch tracers. We discuss briefly the prospect of using this new tool to constrain detailed models of Galactic formation and evolution.

The bipolar jet of the symbiotic star R Aquarii: A study of its morphology using the high-resolution HST WFC3/UVIS camera

Context. R Aqr is a symbiotic binary system consisting of a Mira variable with a pulsation period of 387 days and a hot companion which is presumably a white dwarf with an accretion disk. This binary system is the source of a prominent bipolar gaseous outflow. Aims. We use high spatial resolution and sensitive images from the Hubble Space Telescope (HST) to identify and investigate the different structural components that form the complex morphology of the R Aqr jet. Methods. We present new high-resolution HST WFC3/UVIS narrow-band images of the R Aqr jet obtained in 2013/14 using the [OIII]λ5007, [OI]λ6300, [NII]λ6583, and Hα emission lines. These images also allow us to produce detailed maps of the jet flow in several line ratios such as [OIII]λ5007/[OI]λ6300 and [NII]λ6583/[OI]λ6300 which are sensitive to the outflow temperature and its hydrogen ionisation fraction. The new emission maps together with archival HST data are used to derive and analyse the proper motion of prominent emitting features which can be traced over 20 years with the HST observations. Results. The images reveal the fine gas structure of the jet out to distances of a few tens of arcseconds from the central region, as well as in the innermost region, within a few arcseconds around the stellar source. They reveal for the first time the straight, highly collimated jet component which can be traced to up to ~900 AU in the NE direction. Images in [OIII]λ5007, [OI]λ6300, and [NII]λ6583 clearly show a helical pattern in the jet beams which may derive from the small-scale precession of the jet. The highly collimated jet is accompanied by a wide opening angle outflow which is filled by low excitation gas. The position angles of the jet structures as well as their opening angles are calculated. Our measurements of the proper motions of some prominent emission knots confirm the scenario of gas acceleration during the propagation of the outflow. Finally, we produce several detailed line ratio maps which present a mosaic combined from the large field and the PSF-subtracted inner region. Conclusions. The high signal-to-noise HST WFC3/UVIS images provide powerful tools for the study of the jet morphology and also bring detailed information about the physical jet gas conditions. The simultaneous observations of [OIII], [OI], [NII], and [SII] would allow us to measure basic parameters of the ionised gas in the R Aqr outflow such as electron density, electron temperature and hydrogen ionisation fraction, and compare them with other stellar jets.