Exploring diffuse radio emission in galaxy clusters and groups with the uGMRT and the SKA

Diffuse radio emission has been detected in a considerable number of galaxy clusters and groups, revealing the presence of pervasive cosmic magnetic fields, and of relativistic particles in the large-scale structure (LSS) of the Universe. Since cluster radio emission is faint and steep spectrum, its observations are largely limited by the instrument sensitivity and frequency of observation, leading to a dearth of information, more so for lower-mass systems. The unprecedented sensitivity of recently commissioned low-frequency radio telescope arrays, aided by the development of advanced calibration and imaging techniques, have helped in achieving unparalleled image quality. At the same time, the development of sophisticated numerical simulations and the availability of supercomputing facilities have paved the way for high-resolution numerical modeling of radio emission, and the structure of the cosmic magnetic fields in LSS, leading to predictions matching the capabilities of observational facilities. In view of these rapidly-evolving scenerio in modeling and observations, in this review, we summarise the role of the new telescope arrays and the development of advanced imaging techniques and discuss the detections of various kinds of cluster radio sources. In particular, we discuss observations of the cosmic web in the form of supercluster filaments, studies of emission in poor clusters and groups of galaxies, and of ultra-steep spectrum sources. We also review the current theoretical understanding of various diffuse cluster radio sources and the associated magnetic field and polarization. As the statistics of detections improve along with our theoretical understanding, we update the source classification schemes based on their intrinsic properties. We conclude by summarising the role of the upgraded GMRT and our expectations from the upcoming Square Kilometre Array (SKA) observatories.Comment: 32 pages, 10 figures, accepted for publication in the Journal of Astrophysics and Astronomy (JoAA) (to appear in the special issue on "Indian participation in the SKA"

Stability of Non-asymptotically flat thin-shell wormholes in generalized dilaton-axion gravity

We construct a new type of thin-shell wormhole for non-asymptotically flat charged black holes in generalized dilaton-axion gravity inspired by low-energy string theory using cut-and-paste technique. We have shown that this thin shell wormhole is stable. The most striking feature of our model is that the total amount of exotic matter needed to support the wormhole can be reduced as desired with the suitable choice of the value of a parameter. Various other aspects of thin-shell wormhole are also analyzed.Comment: 15 pages and 11 figures. Minor revisions have been done. Accepted in Int.J.Theor.Phy

Abacarus sundarbanensis Sur & Roy & Chakrabarti 2018, n. sp.

<i>Abacarus sundarbanensis</i> n. sp. <p>(Figs. 1, 2)</p> <p> <b>Diagnosis.</b> Prodorsal shield with complete admedian lines, submedian lines absent, covered with numerous small granules, median line present in posterior 1/3 of prodorsal shield and forms Y-shaped fork meeting admedian lines anteriorly; ridges of dorsal opisthosoma without microtubercles; genital coverflap with 5 transverse lines anteriorly and 4-5 converging, oblique lines posteriorly; empodium 4-rayed.</p> <p> FEMALE (holotype and 19 paratypes): Body fusiform, white coloured, 168 (168–172), 55 (52–56) wide. Gnathosoma—17 (14–17), projecting downward; pedipalp genual setae <i>d</i> 4 (3–4), pedipalp coxal setae <i>ep</i> 2 (2–3). Prodorsal shield—30 (30–31), 51 (48–51) wide, sub-triangular, blunt frontal lobe over gnathosoma, covered with numerous small granules, median line present in posterior 1/3 part of prodorsal shield and forms Y-shaped fork meeting admedian lines anteriorly, admedian lines complete, sinuate with transverse line at anterior 1/3 part of prodorsal shield, submedian lines absent; sub-cylindrical scapular tubercles 5 (4–5) at rear shield margin, 23 (21– 23) apart, scapular setae <i>sc</i> 19 (18–20) and directed posteriorly. Leg I—from base of trochanter 26 (26–28), femur 7 (7–9), basiventral femoral seta <i>bv</i> 12 (11–12); genu 3 (3–4), antaxial genual setae <i>l″</i> 26 (25–26); tibia 5 (4–5), paraxial tibial setae <i>l ′</i> 12 (11–12); tarsus 7 (6–7), paraxial fastigial tarsal setae <i>ft ′</i> 18 (18–19), antaxial fastigial tarsal setae <i>ft″</i> 15 (15–17), paraxial unguinal tarsal setae <i>u ′</i> 4 (4–5); tarsal empodium em 5 (4–5), 4-rayed, tarsal solenidion <i>ω</i> 5 (4–5), curved and blunt. Leg II—from base of trochanter 23 (23–25), femur 8 (7–8), basiventral femoral seta <i>bv</i> 14 (14–16); genu 2 (2–3), antaxial genual setae <i>l″</i> 9 (8–9); tibia 4 (3–4), paraxial tibial setae <i>l ′</i> absent; tarsus 5 (5–7), paraxial fastigial tarsal setae <i>ft ′</i> 19 (18–20), antaxial fastigial tarsal setae <i>ft″</i> 10 (9–10), paraxial unguinal tarsal setae <i>u ′</i> 3 (3–4); tarsal empodium em 5 (4–5), 4-rayed, tarsal solenidion <i>ω</i> 6 (6–8), curved and blunt. Prosternal apodeme indistinct. Coxae I—13 (13–15) with small granules; anterolateral setae on coxisternum I <i>1</i> b 4 (4–5) and 9 (8–9) apart; proximal setae on coxisternum I <i>1a</i> 9 (9–10) and 9 (8–9) apart; coxae II—11 (11–12) with fewer granules than coxae I, base of coxal setae with few small curved lines, proximal setae on coxisternum II <i>2</i> a 34 (34–36) and 23 (22–23) apart, setae <i>1a</i> located well anterior to <i>2a</i>. Opisthosoma—with 65 (64–67) dorsal annuli forming three ridges, median ridge extends from 3rd (2nd–3rd) annulus to 40th (38th–42nd) annulus and ends in a dorsal furrow, lateral ridges extend from 2nd (1st–2nd) annulus to 51st (48th–52nd) annulus; 64 (64–68) ventral annuli with rounded microtubercles till 53rd annuli and microstriation present on last 14 annuli; setae <i>c2</i> 30 (30–35) on ventral annulus 8 (8–9); setae <i>d</i> 55 (54–55) on ventral annulus 19 (18–19); setae <i>e</i> 60 (58– 60) on ventral annulus 40 (38–40); setae <i>f</i> 20 (20–25) on ventral annulus 61 (61–63); setae <i>h1</i> 4 (3–4), setae <i>h2</i> 32 (32–36). Genital coverflap—13 (13–15), 19 (19–21) wide, with five transverse lines at basal part and distal striae forming one small longitudinal line at centre and 5 (4–5) diagonal lines on either side, converging posteriorly, proximal setae on coxisternum III <i>3a</i> 16 (13–17). Internal genitalia—apodeme curved, spermathecal duct short, spermathecae long and rounded.</p> <p>MALE: Not observed.</p> <p> <b>Type material</b>. Holotype: Female (marked) on slide (no. 1888/191/2017), <b>INDIA</b>: West Bengal, Jharkhali, Sundarban, South 24 Paraganas, 22˚03′ N, 88˚70′ E, altitude 40 m, 30 March, 2017 on <i>Pongamia glabra</i> (Fabaceae), coll. S. Roy. Paratypes: 9 females on 4 slides; (nos. 1889-1892 /191/2017) collection data same as holotype; 10 females and 9 nymphs on 8 slides (nos. 1905-1912 /240/2017), 25 December, 2017, collected from the above plant from the same locality, coll. S. Roy & S. Sur.</p> <p> <b>Relation to host</b>. The white coloured mites are vagrant on the under-surfaces of leaves.</p> <p> <b>Etymology</b>. The specific epithet is masculine gender and is derived from the locality of the specimens collected.</p> <p> <b>Remarks</b>. <i>Abacarus sundarbanensis</i> <b>n. sp.</b> comes very close to <i>Abacarus gossypii</i> Mohanasundaram, 1982 in having a genital flap with horizontal lines on the basal part and distal striae with one longitudinal line in the centre, granular coxae, all normal leg setae and simple tarsal solenidion <i>ω</i>. However, <i>A</i>. <i>sundarbanensis</i> is distinct from the latter by the presence of complete admedian lines and absence of submedian lines on the prodorsal shield, 4- rayed empodium, absence of microtubercles on the ridges of the dorsal opisthosoma, and distal scorings with 5 (4- 5) lines on genital coverflap (whereas short admedian lines and three submedian lines on each side of prodorsal shield, 5-rayed empodium, microtubercles on ridges of dorsal opisthosoma, and distal scorings with 10 lines on genital coverflap in <i>A. gossypii</i>).</p>Published as part of <i>Sur, Surajit, Roy, Sourav & Chakrabarti, Samiran, 2018, Two new eriophyoid mites (Acari: Eriophyoidea) from West Bengal, India, pp. 193-200 in Zootaxa 4434 (1)</i> on pages 194-196, DOI: 10.11646/zootaxa.4434.1.13, <a href="http://zenodo.org/record/1290926">http://zenodo.org/record/1290926</a&gt

Two new eriophyoid mites (Acari: Eriophyoidea) from West Bengal, India

Sur, Surajit, Roy, Sourav, Chakrabarti, Samiran (2018): Two new eriophyoid mites (Acari: Eriophyoidea) from West Bengal, India. Zootaxa 4434 (1): 193-200, DOI: https://doi.org/10.11646/zootaxa.4434.1.1

New genera, a new species, and a key to the genera of Ashieldophyinae (Acari, Eriophyoidea) from India

Two new genera, Brevishieldophyes Chakrabarti & Pandit, gen. n. and Mesoshieldophyes Chakrabarti & Pandit, gen. n., and a new species Mesoshieldophyes varecae Chakrabarti & Pandit, sp. n. are described. These mites are leaf vagrants. The morphological characters of the afore-mentioned genera and those of Ashieldophyes Mohanasundaram are compared. A key for separating the genera within the subfamily Ashieldophyinae is provided. The diagnostic characters of the subfamily Ashieldophyinae are also revised

New genera, a new species, and a key to the genera of Ashieldophyinae (Acari, Eriophyoidea) from India

Two new genera, Brevishieldophyes Chakrabarti & Pandit, gen. n. and Mesoshieldophyes Chakrabarti & Pandit, gen. n., and a new species Mesoshieldophyes varecae Chakrabarti & Pandit, sp. n. are described. These mites are leaf vagrants. The morphological characters of the afore-mentioned genera and those of Ashieldophyes Mohanasundaram are compared. A key for separating the genera within the subfamily Ashieldophyinae is provided. The diagnostic characters of the subfamily Ashieldophyinae are also revised

Diptilomiopus integrifoliae Mohanasundaram 1981

Diptilomiopus integrifoliae Mohanasundaram, 1981 Diptilomiopus integrifoliae Mohanasundaram, 1981, Oriental insects, 15 (1): 49-51. Diptilomiopus holoptelus Chakrabarti and Mondal, 1983, Acarologia, XXIV (3): 302-303.Published as part of Chakrabarti, Samiran, Sur, Surajit & Sarkar, Sanjay, 2019, Two new species of Diptilomiopus Nalepa (Acari: Eriophyoidea) from India, pp. 383-394 in Acarologia 59 (3) on page 392, DOI: 10.24349/acarologia/20194337, http://zenodo.org/record/517371