Detailed studies of IPHAS sources - III. The highly extinguished bipolar planetary nebula IPHASX J191104.8+060845

We present the first detailed study of the bipolar planetary nebula (PN) IPHASX J191104.8+060845 (PN G 040.6−01.5) discovered as part of the Isaac Newton Telescope Photometric Hα Survey of the Northern Galactic plane (IPHAS). We present Nordic Optical Telescope (NOT) narrow-band images to unveil its true morphology. This PN consists of a main cavity with two newly uncovered extended low-surface brightness lobes located towards the NW and SE directions. Using near-IR WISE images we unveiled the presence of a barrel like structure, which surrounds the main cavity, which would explain the dark lane towards the equatorial regions. We also use Gran Telescopio de Canarias (GTC) spectra to study the physical properties of this PN. We emphasise the potential of old PNe detected in IPHAS to study the final stages of the evolution of the circumstellar medium around solar-like stars.

Studying star-forming processes at core and clump scales: the case of the young stellar object G29.862−0.0044

Aims. To advance our knowledge of star formation, in addition to statistical studies and large surveys of young stellar objects (YSOs), it is important to carry out detailed studies towards particular objects. Given that massive molecular clumps fragment into cores where star formation takes place, these kinds of studies should be done on different spatial scales. The aim of this work is to investigate the star-forming processes at core and clump scales. Methods. Using near-infrared (NIR) data obtained with NIRI at the Gemini-North telescope, data of the complex molecular species CH3OCHO and CH3CN obtained from the Atacama Large Millimeter Array (ALMA) database, observations of HCN, HNC, HCO+, and C2H carried out with the Atacama Submillimeter Telescope Experiment (ASTE), and CO data from public surveys observed with the James Clerck Maxwell Telescope (JCMT), we perform a deep study of the YSO G29.862−0.0044 (YSO-G29) at core and clump spatial scales. Results. The NIR emission shows that YSO-G29 is composed of two nebulosities separated by a dark lane, suggesting a scenario consistent with a typical disc plus jets system, albeit in this case highly asymmetric. The northern nebulosity is open, diffuse, and is divided into two branches, while the southern one is smaller and sharper. They are likely produced by the scattered light in cavities carved out by jets or winds on an infalling envelope of material, which also presents line emission of H2 S(1) 1–0 and 2–1, and [FeII]. The presence of the complex molecular species observed with ALMA confirms that we are mapping a hot molecular core. The CH3CN emission concentrates at the position of the dark lane and appears slightly elongated from southwest to northeast in agreement with the inclination of the system as observed in the NIR. The morphology of the CH3OCHO emission is more complex and extends along some filaments and concentrates in knots and clumps, mainly southwards of the dark lane, suggesting that the southern jet is encountering a dense region. The northern jet is able to flow more freely, generating the more extended features as seen in the NIR. This is in agreement with the redshifted molecular outflow traced by the 12CO J = 3–2 line extending towards the northwest and the lack of a blueshifted outflow. This configuration can be explained by considering that G29-YSO is located at the furthest edge of the molecular clump along the line of sight, which is consistent with the position of the source in the cloud mapped in the C18O J = 3–2 line. The detection of HCN, HNC, HCO+, and C2H allowed us to characterise the dense gas at clump scales, yielding results that are in agreement with the presence of a high-mass protostellar object.

When Nothing Is True, Everything Is Possible: On Truth and Power by Way of Socialist Realism

In this essay, i contend that our current crisis of truth, however distressing, is a replay of an earlier one that saw a far-reaching, devastating destruction of truth. The simultaneous recrudescence of right-wing populism and dawn of the post-truth age recall the way totalitarian movements in the twentieth century exposed the masses to organized lying. Today, the plague of so-called alternative facts and fake news, while incubated and spread by digital technology, can, like totalitarianism's organized lies, be traced back to the erosion of democratic institutions and the loss of faith in democracy's foundational narratives. To understand how our contemporary politics could be going down the dark lane of history again, I turn to the political philosophy of Claude Lefort, Anthony Giddens, and Hannah Arendt, who have written perspicaciously on what happens to truth when the citizenry collectively disinvests from common knowledge and disbelieves in the common good.

Nobeyama 45 m mapping observations toward Orion A. II. Classification of cloud structures and variation of the 13CO/C18O abundance ratio due to far-UV radiation

We present results of the classification of cloud structures toward the Orion A Giant Molecular Cloud based on wide-field 12CO (J = 1–0), 13CO (J = 1–0), and C18O (J = 1–0) observations using the Nobeyama 45 m radio telescope. We identified 78 clouds toward Orion A by applying Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) to the data cube of the column density of 13CO. Well-known subregions such as OMC-1, OMC-2/3, OMC-4, OMC-5, NGC 1977, L1641-N, and the dark lane south filament (DLSF) are naturally identified as distinct structures in Orion A. These clouds can also be classified into three groups: the integral-shaped filament, the southern regions of Orion A, and the other filamentary structures in the outer parts of Orion A and the DLSF. These groups show differences in scaling relations between the physical properties of the clouds. We derived the abundance ratio between 13CO and C18O, $X_{^{13}\mathrm{CO}}/X_{\mathrm{C}^{18}\mathrm{O}}$, which ranges from 5.6 to 17.4 on median over the individual clouds. The significant variation of $X_{^{13}\mathrm{CO}}/X_{\mathrm{C}^{18}\mathrm{O}}$ is also seen within a cloud in both the spatial and velocity directions and the ratio tends to be high at the edge of the cloud. The values of $X_{^{13}\mathrm{CO}}/X_{\mathrm{C}^{18}\mathrm{O}}$ decrease from 17 to 10 with the median of the column densities of the clouds at the column density of $N_{\mathrm{C^{18}O}} \gtrsim 1 \times 10^{15}\:$cm−2 or visual extinction of AV ≳ 3 mag under the strong far-ultraviolet (FUV) environment of G0 > 103, whereas it is almost independent of the column density in the weak FUV radiation field. These results are explained if the selective photodissociation of C18O is enhanced under a strong FUV environment and it is suppressed in the dense part of the clouds.

Planetary nebulae with UVIT

The high excitation planetary nebula, NGC 6302, has been imaged in two far-ultraviolet (FUV) filters, F169M (Sapphire; λeff: 1608 Å) and F172M (Silica; λeff: 1717 Å) and two near-UV (NUV) filters, N219M (B15; λeff: 2196 Å) and N279N (N2; λeff: 2792 Å) with the Ultra Violet Imaging Telescope (UVIT). The FUV F169M image shows faint emission lobes that extend to about 5 arcmin on either side of the central source. Faint orthogonal collimated jet-like structures are present on either side of the FUV lobes through the central source. These structures are not present in the two NUV filters or in the FUV F172M filter. Optical and infrared (IR) images of NGC 6302 show bright emission bipolar lobes in the east-west direction with a massive torus of molecular gas and dust seen as a dark lane in the north-south direction. The FUV lobes are much more extended and oriented at a position angle of 113°. They and the jet-like structures might be remnants of an earlier evolutionary phase, prior to the dramatic explosive event that triggered the Hubble type bipolar flows approximately 2200 years ago. The source of the FUV lobe and jet emission is not known, but is likely due to fluorescent emission from H2 molecules. The cause of the difference in orientation of optical and FUV lobes is not clear and, we speculate, could be related to two binary interactions.

Anatomy of the massive star-forming region S106

The central area (40″ × 40″) of the bipolar nebula S106 was mapped in the [O I] line at 63.2 μm (4.74 THz) with high angular (6″) and spectral (0.24 MHz) resolution, using the GREAT heterodyne receiver on board SOFIA. The spatial and spectral emission distribution of [O I] is compared to emission in the CO 16 →15, [C II] 158 μm, and CO 11 →10 lines, mm-molecular lines, and continuum. The [O I] emission is composed of several velocity components in the range from –30 to 25 km s−1. The high-velocity blue- and red-shifted emission (v = −30 to –9 km s−1 and 8 to 25 km s−1) can be explained as arising from accelerated photodissociated gas associated with a dark lane close to the massive binary system S106 IR, and from shocks caused by the stellar wind and/or a disk–envelope interaction. At velocities from –9 to –4 km s−1 and from 0.5 to 8 km s−1 line wings are observed in most of the lines that we attribute to cooling in photodissociation regions (PDRs) created by the ionizing radiation impinging on the cavity walls. The velocity range from –4 to 0.5 km s−1 is dominated by emission from the clumpy molecular cloud, and the [O I], [C II], and high-J CO lines are excited in PDRs on clump surfaces that are illuminated by the central stars. Modelling the line emission in the different velocity ranges with the KOSMA-τ code constrains a radiation field χ of a few times 104 and densities n of a few times 104 cm−3. Considering self-absorption of the [O I] line results in higher densities (up to 106 cm−3) only for the gas component seen at high blue- and red velocities. We thus confirm the scenario found in other studies that the emission of these lines can be explained by a two-phase PDR, but attribute the high-density gas to the high-velocity component only. The dark lane has a mass of ~275 M⊙ and shows a velocity difference of ~1.4 km s−1 along its projected length of ~1 pc, determined from H13CO+ 1 →0 mapping. Its nature depends on the geometry and can be interpreted as a massive accretion flow (infall rate of ~2.5 × 10−4 M⊙ yr−1), or the remains of it, linked to S106 IR/FIR. The most likely explanation is that the binary system is at a stage of its evolution where gas accretion is counteracted by the stellar winds and radiation, leading to the very complex observed spatial and kinematic emission distribution of the various tracers.

A Tough Egg to Crack

The sculpting of the Egg Nebula continues to defy a coherent explanation. Bipolar outflows from the center of the nebula have created bipolar optical lobes that are illuminated by searchlight beams; multiple bipolar outflows orthogonal to the lobes create the appearance of a dark lane; and quasi-circular arcs are imprinted on an approximately spherically-symmetric wind from the progenitorAGB-star. Here, we use archival data from ALMA to study at high angular resolution dust and molecular gas at the center of the nebula. We find that: (i) dust is concentrated in multiple blobs that outline the base of the northern optical lobe; (ii) dense molecular gas forms the wall of a channel swept up and compressed by the outflows that created the bipolar optical lobes; (iii) the expansion and illumination center of the nebula lies at or close to center of the outflow channel. We present a simple working model for the Egg Nebula, and highlight the difficulties that any model face for explaining all the features seen in this nebula.

The formation of an equatorial coronal hole

The formation of an equatorial coronal hole (CH) from 2006 January 9 to 12 was simultaneously observed byGOES-12/SXI,SOHO/EIT andSOHO/MDI instruments. The varieties of soft X-ray and EUV brightness, coronal temperature, and total magnetic flux in the CH were examined and compared with that of a quiet-sun (QS) region nearby. The following results are obtained. (1) A preexisting dark lane appeared on the location of the followed CH and was reinforced by three enhanced networks. (2) The CH gradually formed in about 81 hours and was predominated by positive magnetic flux. (3) During the formation, the soft X-ray and EUV brightness, coronal temperature, and total magnetic flux obviously decreased in the CH, but were almost no change in the QS region. The decrease of the total magnetic flux may be the result of magnetic reconnection between the open and closed magnetic lines, probably indicating the physical mechanism for the birth of the CH.