Half Light Research Articles

Educación, pensamiento complejo y ciudad: La categoría de comunidad en la crónica Medellín, bajo el milagro de la media luz (1983) de Juan José Hoyos Naranjo

In the following reflection article, whose connotation is educational; it is considered to address the analysis of the chronicle “Medellín, under the miracle of the half light” (1993) by the writer Juan José Hoyos Naranjo. The chronicle presents a narrative impregnated with orality and marked by complex discursive procedures. In that sense, said analysis will focus on education from the Morinian thought and the concept of community. Hoyos’ work intertwines enjoyment and nostalgia, offering a deep understanding of how communities have intervened in the transformations of Medellín. As a careful observer of his city, Hoyos uses everyday elements such as bars, objects and the urban environment to capture the essence of Medellín and outline the profile of the urban subject. His critical approach exposes both public and biographical aspects, especially his experience as a journalist in the 1980s, a period in which he faced, as a reporter, the power dynamics of drug trafficking and the drastic urban changes of the city. This chronicle not only documents these events, but also derives from his journalistic work, consolidating itself as a piece that merges his professional career with a critical and personal vision of the evolution of Medellín. Aspect that is expanded in the perspective of Complex thinking with a focus on the category of community.

Dwarf galaxies as a probe of a primordially magnetized Universe

Aims. The true nature of primordial magnetic fields (PMFs) and their role in the formation of galaxies remains elusive. To shed light on these unknowns, we investigated their impact by varying two sets of properties: (i) accounting for the effect of PMFs on the initial matter power spectrum and (ii) accounting for their magneto-hydrodynamical effects on the formation of galaxies. By comparing both, we can determine the dominant agent in shaping galaxy evolution. Methods. We used the magneto-hydrodynamics code RAMSES to generate multiple new zoom-in simulations for eight different host halos of dwarf galaxies across a wide luminosity range of 103 − 106 L⊙. These halos were selected from a ΛCDM cosmological box, tracking their evolution down to redshift z = 0. We explored a variety of primordial magnetic field (comoving) strengths of Bλ ranging from 0.05 to 0.50 nG. Results. We find that magnetic fields in the interstellar medium not only modify star formation processes in dwarf spheroidal galaxies, but these fields also entirely prevent the formation of stars in less compact, ultra-faint galaxies with halo masses and stellar masses below, respectively, ∼2.5 × 109 and 3 × 106 M⊙. At high redshifts, the impact of PMFs on host halos of dwarf galaxies through the modification of the matter power spectrum is more dominant than the influence of magneto-hydrodynamics in shaping their gaseous structure. Through the amplification of small perturbations ranging in mass from 107 to 109 M⊙ in the ΛCDM+PMFs matter power spectrum, primordial fields expedite the formation of the first dark matter halos, leading to an earlier onset and a higher star formation rate at redshifts of z > 9. We investigated the evolution of various energy components and demonstrated that magnetic fields with an initial strength of Bλ ≥ 0.05 nG exhibit a strong growth of magnetic energy, accompanied by a saturation phase that begins soon after the growth phase. These trends persist consistently, regardless of the initial conditions or whether it is the classical ΛCDM model or ΛCDM modified by PMFs. Lastly, we investigated the impact of PMFs on the present-time observable properties of dwarf galaxies, namely: the half light radius, V-band luminosity, mean metallicity, and velocity dispersion profile. We find that PMFs with moderate strengths of Bλ ≤ 0.10 nG show an impressive agreement with the scaling relations of the observed Local Group dwarfs. However, stronger fields lead to larger sizes and higher velocity dispersions.

Benefits of Intelligent Fuzzy Controllers in Comparison to Classical Methods for Adaptive Optics

Adaptive Optics (AO) systems have been developed throughout recent decades as a strategy to compensate for the effects of atmospheric turbulence, primarily caused by poor astronomical seeing. These systems reduce the wavefront distortions using deformable mirrors. Several AO simulation tools have been developed, such as the Object-Oriented, MATLAB, and Adaptive Optics Toolbox (OOMAO), to assist in the project of AO. However, the main AO simulators focus on AO models, not prioritizing the different control techniques. Moreover, the commonly applied control strategies in ground-based telescopes are based on Integral (I) or Proportional-Integral (PI) controllers. This work proposes the integration of OOMAO models to Simulink to support the development of advanced controllers and compares traditional controllers with intelligent systems based on fuzzy logic. The controllers were compared in three scenarios of different turbulence and atmosphere conditions. The simulations were performed using the characteristics/parameters of the Southern Astrophysical Research (SOAR) telescope and assessed with the Full Width at Half Maximum (FWHM), Half Light Radius (HLR), and Strehl ratio metrics to compare the performance of the controllers. The results demonstrate that adaptive optics can be satisfactorily simulated in OOMAO adapted to Simulink and thus further increase the number of control strategies available to OOMAO. The comparative results between the MATLAB script and the Simulink blocks designed showed a maximum relative error of 3% in the Strehl ratio and 1.59% in the FWHM measurement. In the assessment of the control algorithms, the fuzzy PI controller reported a 25% increase in the FWHM metrics in the critical scenario when compared with open-loop metrics. Furthermore, the fuzzy PI controller outperformed the results when compared with the I and PI controllers. The findings underscore the constraints of conventional control methods, whereas the implementation of fuzzy-based controllers showcases the promise of intelligent approaches in enhancing control performance under challenging atmospheric conditions.

Ethical AI does not have to be like finding a black cat in a dark room

Ethical AI does not have to be like finding a black cat in a dark room

Dramatic Monologue in Bidart’s Work “Half-Light” (2017)

This paper aims at investigating dramatic monologue in Frank Bidart’s poems. It discusses the way Bidart was affected by certain poets in terms of the implication of the dramatic monologue device and the power that affected his implementation and his application of this particular genre. Bidart proposes that a poet has a lot of inner consciousness. He receives various voices so he can visualize how to begin from varied places and keep a certain distance from the voice that expresses out of its sense, agony, or annoyance. Bidart has to examine the reasons for definite feelings at a particular point in time because one’s emotional state should not be considered for granted. However, a poet should keep some distance from the characters in the poem as well as keep a sort of skepticism concerning oneself. This study suggests that Bidart’s dramatic monologue is a contemporary genre that is significantly established at the last stage of his script with the release of his poetic work “Half Light”. The study analysed two poems of Bidart’s work including Old and Young, and Thirst. Results of the study showed that Bidart’s poetic forms and themes relate to many issues including the point of time in which the poet published his poems, the setting and situations, and the poet’s psychological state of mind.

Liberation: Shiv Tattva, and: Liberation: Summit, and: The Goddess Incarnates, and: Cow Dust Hour, and: Emancipation

Liberation: Shiv Tattva, and: Liberation: Summit, and: The Goddess Incarnates, and: Cow Dust Hour, and: Emancipation Nidhi Agrawal (bio) Shiv Tattva On some days,I am Sati.On some days,I am Parvathi.You created me and filled me withMaya (Illusion).Set me free.I offer my sins (Pap) and piety (Punya)At your feet to becomeEmpty and hollow.Will you become Gunagrahin (Acceptor of gunas) to consume my righteousness?I ask you,Will you become Hara (Remover of sins)To cleanse your creation?I am your Sati,I am your Parvathi.You have to liberate me from the cycle ofBirth and Death,Only then,Shiva Tattva will blossomBetween us, Shiva! Summit Enough of preying on my flesh.Sucking my bloodWon't take you to heaven.When your fervor devour is done,Kali will consume you. [End Page 75] The Goddess Incarnates At midnight, on a seat of five skullsI worship the slayer of illusions,The Maharaja (King) gifted me thirty—threeAcres of rent—free earth, 1I have planted seeds of your devotion (Bhakti)In the soil of my bones to perform corpse rituals.The world calls me mother—crazy and love—mad,Your status comes alive in my skeleton,Oh, Mother Kali! Tell meIf the Goddess incarnates. [End Page 76] Cow Dust Hour I dwell on the ferocious cremation groundsYearning for my Mother Kali!She carries waxing gibbous on her forehead,The Sun grows larger in her right pupil,The Moon drips from the two corners of her left eye,She burns the demons in the catacomb of her three eyes.You cannot carry her consort in your palm,He keeps her love and fury in the ocean of his heart. I am restless, this longing to meet myMother will swallow me.Oh, Mother! I have transposed to a ghoulYour disciples are my friends now.They claim,Between the day and night–When twilight rises to the throat of the sky,The hours of Sun and darkness make love,There is no period of half—light,I will meet you at,The time of Union. [End Page 77] Emancipation My eyes brim with the weight of dusk,Emotions conflagrate in my heartBurning the corpse without fuel.This dawn I am returning to my houseTo constellate my belongings. The entrance is clouded by theScattered scars of my childhood,Every drawer is sealed with the secrets ofMy disappointments.Today, I let go of my failures and riseFrom the floor,As soot rises from the throat.With every effort to clean the houseMy spine travels to the nucleus of my brainShowing me the way to the bedroom. At the bedroom's door,I stand startled by the view.The Mother Goddess is coming togetherWith the God of Mountains,Consuming my form and liberating meFrom prison. Nidhi Agrawal nidhi agrawal has a background in communication design in health, media and entertainment spaces. She strongly feels that poetry is a deal of joy, she is the author of the poetry collection, "Confluence". Her work has been published in California State Poetry Society, University of Tennessee, Chronogram Media, Yale University, South Asian Today, Indian Periodical, Spill Words Press, Rising Phoenix Review, and Setu Journal, and elsewhere. She lives in Bihar, India. notes 1. Ramprasad Sen, (flourished 18th century), Shakta poet-saint of Bengal. Ramprasad is reputed to have composed some 100,000 songs, some of which became extremely popular among his followers, who regard them as sacred mantras. The goddess Ramprasad portrays is sometimes beautiful, nurturing, and even erotic and at other times grotesque, dangerous, and fickle. Ramprasad contributed to a revival of Shaktism and Tantrism in Bengal and also, in the wake of increased Western presence in India, identified the goddess with Moses and Jesus as well as with the Hindu deities. Copyright © 2023 University of North Dakota

Why I Gave My Harness Bells a Shake, and: Cricket in the House, and: Trespasses, and: Interregnum

Why I Gave My Harness Bells a Shake, and: Cricket in the House, and: Trespasses, and: Interregnum Benjamin S. Grossberg (bio) Why I Gave My Harness Bells a Shake My little horse must think it queer … I knew that there was no mistake. We were alwaysstopping, and not, of course, for my convenience.Not that I mind a good canter in winter, especiallylate mornings, the sun reflecting up from a snowyroad, the feel of my hooves breaking its crust—and even better once I get moving: justhoof crunch, harness bell, wind and downy flakerushing past my ears. In those moments, youforget the driver and being driven. Forget eventhe effort of motion: you're just anothermoving thing, the wind like a water currentpushing you on. But our rides were rarely like that. For one thing, they were freighted by promises.How his promises became my problem, I'm not sure,but, by harness and whip, they did. (He didn't oftenmention the whip.) We'd start after sunset,guaranteeing a late return, with little timeto wipe me down. I'd shiver to sleep underrough wool, watching his lantern disappearbehind a barn door. And they'd drive us farinto north country, those promises, him withparcels or packets of letters, slipping insidefor a while, only to return laughing, breath richwith coffee, sugar, usually brandy. I'd smell it [End Page 74] when he'd come alongside, a white puffin my face as he checked the bit and pattedmy side before lifting a foot to the cart stepand heaving himself up. My point is, when hewanted to stop, we did. My concerns: a horseof a different color. There were spots beautifulto me, too. I got enough of fields filling with snow.But sometimes sunset—late August hazeturning purple over evergreens. Or a river,the cool bubbling on my hoofs, just imagining it.And orchards: October studding the groundwith windfalls, halving one with a single crunch and feeling the drip down my chin, licking my tonguearound my sticky muzzle—that is, if I wasn'twearing a bit, and, of course, if we had stopped.Bottom line: I shook the bells because I wantedto get home. Oat bag, blanket, straw mound:eyes closing. Once, years ago, at the edgeof my pasture, I saw a man: mid-forties, careworn,lingering at the fence, and when I wandered over,he extended his arm to me, palm facing up.In it: four cubes of sugar. Like dice, like we wereabout to make a bet. I knew, I understood at onceto bite gently, with just the edge of my teeth. My lips brushing his calloused palm, my nostrilsfilling with dark sugar and human sweat—I sometimes recall it, that singular touch, before I sleep. Cricket in the House Not the music. Like a bicycle bellringing faster as you pedal faster.Not the spring-set contraption [End Page 75] of its body, which I expected to be bigas a mantis but could sit comfortablyon a nickel. No, not in the half light,how its trilling turns the roominto a field at dusk in which someone'sset a couch, a coffee table, a wingback.And not transformations generally:sound making space like the time I bustedan eardrum and brought, to the silenceof my bedroom, the shushing of a distantocean. Not like that. And nothow it got in. Or how long it would beuntil and why it would die. Just whatdo they eat and drink, anyway? Butthe thought of music meant for othersof its kind now backed behind a couchon hardwoods, antiseptic and dry—a patina of dust, cobwebsat the legs, and cat-hair tumbleweedsas I cross the room and it falls silent,the cricket, briefly. And how it mustlong for mud and coolness, for the dewnight covers everything with, for allthe other sounds insects make thatI don't notice but that it notices, howit must register dislocation, evenisolation...

UV and NIR size of the low-mass field galaxies: the UV compact galaxies

Context. Most of the massive star-forming galaxies are found to have “inside-out” stellar mass growth modes, which means the inner parts of the galaxies mainly consist of the older stellar population, while the star forming in the outskirt of the galaxy is still ongoing. Aims. The high-resolution HST images from Hubble Deep UV Legacy Survey and Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey projects with the unprecedented depth in both F275W and F160W bands are the perfect data sets to study the forming and formed stellar distribution directly. Methods. We selected the low redshift (0.05 < zspec < 0.3) galaxy sample from the GOODS-North field where the HST F275W and F160W images are available. Then we measured the half light radius in F275W and F160W bands, which are the indicators of the star formation and stellar mass. Results. By comparing the F275W and F160W half light radius, we find the massive galaxies are mainly follow the “inside-out” growth mode, which is consistent with the previous results. Moreover, the HST F275W and F160W images reveal that some of the low-mass galaxies (< 108 M⊙) have the “outside-in” growth mode: their images show a compact UV morphology, implying an ongoing star formation in the galaxy centre, while the stars in the outskirts of the galaxies are already formed. The two modes transit smoothly at stellar mass range about 108 − 9 M⊙ with a large scatter. We also try to identify the possible neighbour massive galaxies from the SDSS data, which represent the massive galaxy sample. We find that all of the spec-z selected galaxies have no massive galaxy nearby. Thus the “outside-in” mode we find in the low-mass galaxies are not likely originated from the environment.

An old, metal-poor globular cluster in Sextans A and the metallicity floor of globular cluster systems

We report the confirmation of an old, metal-poor globular cluster in the nearby dwarf irregular galaxy Sextans A, the first globular cluster known in this galaxy. The cluster, which we designate as Sextans A-GC1, lies some 4.4 arcminutes ($\sim1.8$ kpc) to the SW of the galaxy centre and clearly resolves into stars in sub-arcsecond seeing ground-based imaging.We measure an integrated magnitude $V=18.04$, corresponding to an absolute magnitude, $M_{V,0} = -7.85$. This gives an inferred mass $M\sim$1.6$\times10^5~M\odot$, assuming a Kroupa IMF. An integrated spectrum of Sextans A-GC1 reveals a heliocentric radial velocity $v_{\rm helio}=305\pm15$~ km/s, consistent with the systemic velocity of Sextans A. The location of candidate red giant branch stars in the cluster, and stellar population analyses of the cluster's integrated optical spectrum, suggests a metallicity [Fe/H] $\sim$--2.4, and an age $\sim9$ Gyr. We measure a half light radius, $R_h = 7.6\pm0.2$ pc. Normalising to the galaxy integrated magnitude, we obtain a $V$-band specific frequency, $S_N=2.1$. We compile a sample of 1,928 GCs in 28 galaxies with spectroscopic metallicities and find that the low metallicity of Sextans A-GC1 is close to a "metallicity floor" at [Fe/H] $\sim-2.5$ seen in these globular cluster systems which include the Milky Way, M31, M87 and the Large Magellanic Cloud. This metallicity floor appears to hold across 6 dex in host galaxy stellar mass and is seen in galaxies with and without accreted GC subpopulations.

GEP I: A globular cluster in the center of the dwarf spheroidal galaxy Andromeda XXV?

AbstractLooking for variable stars in the M31 dwarf spheroidal satellite Andromeda XXV (And XXV), which we have observed with the LBC at the LBT, we serendipitously discovered a clustering of stars (Gep I) of 12 arcsec in diameter, near the center of And XXV. This is one of the very few clusters known to be associated with a dwarf spheroidal galaxy. The half light radius (rh) of Gep I at the distance of And XXV corresponds to 25 pc in linear extension. Radius and absolute V (MV∼ −4.9 mag) magnitude place Gep I in the region of the MV-rh plane that seems to be forbidden to ordinary globular clusters (GCs). The seeing-limited resolution of our photometry could resolve only a few bright stars in Gep I. The CMD of these sources is compatible with an old stellar population placed at a heliocentric distance of ∼750–800 kpc, thus confirming a real concentration of old stars. The ground-based CMD of Gep I is severely incomplete. Future high resolution imaging and spectroscopy of the brightest stars will permit to disentangle the puzzle on the real nature of Gep I.

Evidence of a Flat Outer Rotation Curve in a Star-bursting Disk Galaxy at z = 1.6

Abstract Observations of the baryon to dark matter fraction in galaxies through cosmic time are a fundamental test for galaxy formation models. Recent observational studies have suggested that some disk galaxies at z > 1 host declining rotation curves, in contrast with observations of low redshift disk galaxies where stellar or H i rotation curves flatten at large radii. We present an observational counterexample, a galaxy named DSFG850.95 at z = 1.555 (4.1 Gyr after the big bang) that hosts a flat rotation curve between radii of ∼6–14 kpc (1.2–2.8 disk scale lengths) and has a dark matter fraction of 0.44 ± 0.08 at the H-band half light radius, similar to the Milky Way. We create position–velocity and position–dispersion diagrams using Keck/MOSFIRE spectroscopic observations of Hα and [N ii] emission features, which reveal a flat rotation velocity of V flat = 285 ± 12 km s−1 and an ionized gas velocity dispersion of σ 0 = 48 ± 4 km s−1. This galaxy has a rotation-dominated velocity field with V flat/σ 0 ∼ 6. Ground-based H-band imaging reveals a disk with Sérsic index of 1.29 ± 0.03, an edge-on inclination angle of 87° ± 2°, and an H-band half light radius of 8.4 ± 0.1 kpc. Our results point to DSFG850.95 being a massive, rotationally supported disk galaxy with a high dark-matter-to-baryon fraction in the outer galaxy, similar to disk galaxies at low redshift.

BÚSQUEDA DE POSIBLES PROGENITORES SIN MATERIA OSCURA DE LA GALAXIA ENANA ESFEROIDAL CARINA A TRAVÉS DE SIMULACIONES DE N-CUERPOS

Se presenta un estudio de la evolución de diferentes posibles progenitores sin materia oscura de la galaxia enana esferoidal Carina, una de las galaxias satélites de la Vía Láctea, mediante simulaciones numéricas Newtonianas de N-Cuerpos. No fue posible reproducir completamente las propiedades observacionales de Carina, y por consiguiente no se pudo determinar un posible progenitor sin materia oscura para la misma; sin embargo, progenitores con masa inicial 1x107 M. y radios de Plummer 0.5 y 0.6 kpc, reprodujeron los valores observacionales de Carina para tres de las cinco variables estudiadas (radio de brillo medio, dispersión de velocidades sobre la visual y distancia galactocéntrica). Por lo tanto estos progenitores podrán ser la base para posteriores trabajos sobre el origen de la galaxia enana Carina.

Local Swift-BAT active galactic nuclei prefer circumnuclear star formation

We use Herschel data to analyze the size of the far-infrared 70 μm emission for z < 0.06 local samples of 277 hosts of Swift-BAT selected active galactic nuclei (AGN), and 515 comparison galaxies that are not detected by BAT. For modest far-infrared luminosities 8.5 <log (LFIR [L⊙]) < 10.5, we find large scatter of half light radii Re,70 for both populations, but a typical Re,70≲ 1 kpc for the BAT hosts that is only half that of comparison galaxies of same far-infrared luminosity. The result mostly reflects a more compact distribution of star formation (and hence gas) in the AGN hosts, but compact AGN heated dust may contribute in some extremely AGN dominated systems. Our findings are in support of an AGN-host coevolution where accretion onto the central black hole and star formation are fed from the same gas reservoir, with more efficient black hole feeding if that reservoir is more concentrated. The significant scatter in the far-infrared sizes emphasizes that we are mostly probing spatial scales much larger than those of actual accretion, and that rapid accretion variations can smear the distinction between the AGN and comparison categories. Large samples are hence needed to detect structural differences that favor feeding of the black hole. No size difference between AGN host and comparison galaxies is observed at higher far-infrared luminosities log(LFIR [L⊙]) > 10.5 (star formation rates ≳6 M⊙ yr-1), possibly because these are typically reached in more compact regions.

The spatially resolved star formation history of CALIFA galaxies

This paper presents the mass assembly time scales of nearby galaxies observed by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record method of the stellar populations to the complete sample of the 3rd CALIFA data release, with a total of 661 galaxies, covering stellar masses from 10$^{8.4}$ to 10$^{12}$ M$_{\odot}$ and a wide range of Hubble types. We apply spectral synthesis techniques to the datacubes and process the results to produce the mass growth time scales and mass weighted ages, from which we obtain temporal and spatially resolved information in seven bins of galaxy morphology and six bins of stellar mass (M$_{\star}$) and stellar mass surface density ($\Sigma_{\star}$). We use three different tracers of the spatially resolved star formation history (mass assembly curves, ratio of half mass to half light radii, and mass-weighted age gradients) to test if galaxies grow inside-out, and its dependence with galaxy stellar mass, $\Sigma_{\star}$, and morphology. Our main results are as follows: (a) The innermost regions of galaxies assemble their mass at an earlier time than regions located in the outer parts; this happens at any given M$_{\star}$, $\Sigma_{\star}$, or Hubble type, including the lowest mass systems. (b) Galaxies present a significant diversity in their characteristic formation epochs for lower-mass systems. This diversity shows a strong dependence of the mass assembly time scales on $\Sigma_{\star}$ and Hubble type in the lower-mass range (10$^{8.4}$ to 10$^{10.4}$), but a very mild dependence in higher-mass bins. (c) All galaxies show negative $\langle$log age$\rangle_{M}$ gradients in the inner 1 HLR. The profile flattens with increasing values of $\Sigma_{\star}$. There is no significant dependence on M$_{\star}$ within a particular $\Sigma_{\star}$ bin, except for the lowest bin, where the gradients becomes steeper.

Discovery of Diffuse Dwarf Galaxy Candidates around M101

Abstract We have conducted a search of a 9 deg2 region of the Canada–France–Hawaii-Telescope Legacy Survey around the Milky Way analog M101 (D ∼ 7 Mpc), in order to look for previously unknown low-surface-brightness galaxies. This search has uncovered 38 new low-surface-brightness dwarf candidates, and confirmed 11 previously reported galaxies, all with central surface brightness μ(g, 0) > 23 mag arcsec−2, potentially extending the satellite luminosity function for the M101 group by ∼1.2 mag. The search was conducted using an algorithm that nearly automates the detection of diffuse dwarf galaxies. The candidates’ small sizes and low surface brightnesses mean that the faintest of these objects would likely be missed by traditional visual or computer detection techniques. The dwarf galaxy candidates span a range of −7.1 ≥ M g ≥ −10.2 and half-light radii of 118–540 pc at the distance of M101, and they are well fit by simple Sérsic surface brightness profiles. These properties are consistent with dwarfs in the Local Group, and to match the Local Group luminosity function, ∼10–20 of these candidates should be satellites of M101. Association with a massive host is supported by the lack of detected star formation and the overdensity of candidates around M101 compared to the field. The spatial distribution of the dwarf candidates is highly asymmetric, and concentrated to the northeast of M101, therefore distance measurements will be required to determine if these are genuine members of the M101 group.

Ejecta mass diagnostics of Type Ia supernovae

We present one-dimensional non-local thermodynamic equilibrium time-dependent radiative transfer simulations (using CMFGEN) of two sub-Chandrasekhar (sub-$M_{\rm Ch}$), one $M_{\rm Ch}$ and one super-$M_{\rm Ch}$ Type Ia SN ejecta models. Three originate from $M_{\rm Ch}$ delayed detonation models, and the fourth is a sub-$M_{\rm Ch}$ detonation model. Ejecta masses are 1.02, 1.04, 1.40, and 1.70 M$_\odot$, and all models have 0.62 M$_\odot$ of $^{56}{\rm Ni}$. Sub-$M_{\rm Ch}$ model light curves evolve faster, reaching bolometric maximum 2--3 days earlier and having 3--4 days shorter bolometric half light widths. The models vary by $\sim$12 per cent at maximum bolometric luminosity and by 0.17 mag in $B_{\rm max}$. While $\Delta M_{15}(B)$ increases with ejecta mass it only varies by $\sim$5 per cent around 1 mag. Sub-$M_{\rm Ch}$ models are 0.25 mag bluer in $B-R$ at $B_{\rm max}$. Optical spectra share many similarities, but lower mass models exhibit less UV line blanketing during the photospheric phase. At nebular times, significant NIR spectroscopic differences are seen. In particular, emission lines of the Ca II NIR triplet; [S III] $\lambda\lambda$9068,9530; [Ca II] $\lambda\lambda$7291,7324; [Ar III] $\lambda\lambda$7135,7751; and [Ni II] 1.939 $\mu$m are stronger in higher mass models. The [Ni II] 1.939 $\mu$m line is absent in the sub-$M_{\rm Ch}$ detonation model, and provides a valuable potential tool to distinguish sub-$M_{\rm Ch}$ explosions from $M_{\rm Ch}$ explosions. In general, the nebular phase models are too highly ionized. We attribute this to the neglect of clumping and/or the distribution of intermediate mass and iron group elements. The two sub-$M_{\rm Ch}$ models, while exploded by different mechanisms, can be distinguished in the $J$ and $H$ bands at late times (e.g., $+200$ days).

The spatially resolved star formation history of mergers

This paper presents the spatially resolved star formation history (2D-SFH) of a small sample of four local mergers: the early-stage mergers IC 1623, NGC 6090, and the Mice, and the more advanced merger NGC 2623, by analyzing IFS data from the CALIFA survey and PMAS in LArr mode. Full spectral fitting techniques are applied to the datacubes to obtain the spatially resolved mass growth histories, the time evolution of the star formation rate intensity (ΣSFR), and the local specific star formation rate (sSFR), over three different time scales (30 Myr, 300 Myr, and 1 Gyr). The results are compared with non-interacting Sbc–Sc galaxies, to quantify if there is an enhancement of the star formation and to trace its time scale and spatial extent. Our results for the three LIRGs (IC 1623 W, NGC 6090, and NGC 2623) show that a major phase of star formation is occurring in time scales of 107 yr to few 108 yr, with global SFR enhancements of between approximately two and six with respect to main-sequence star forming (MSSF) galaxies. In the two early-stage mergers IC 1623 W and NGC 6090, which are between first pericentre passage and coalescence, the most remarkable increase of the SFR with respect to non-interacting spirals occurred in the last 30 Myr, and it is spatially extended, with enhancements of factors between two and seven both in the centres (r < 0.5 half light radius, HLR), and in the disks (r > 1 HLR). In the more advanced merger NGC 2623 an extended phase of star formation occurred on a longer time scale of ~1 Gyr, with a SFR enhancement of a factor of approximately two-to-three larger than the one in Sbc–Sc MSSF galaxies over the same period, probably relic of the first pericentre passage epoch. A SFR enhancement in the last 30 Myr is also present, but only in NGC 2623 centre, by a factor of three. In general, the spatially resolved SFHs of the LIRG-mergers are consistent with the predictions from high spatial resolution simulations. In contrast, the star formation in the Mice, specially in Mice B, is not enhanced but inhibited with respect to Sbc–Sc MSSF galaxies. The fact that the gas fraction of Mice B is smaller than in most non-interacting spirals, and that the Mice are close to a prograde orbit, represents a new challenge for the models, which must cover a larger space of parameters in terms of the availability of gas and the orbital characteristics.

Paving the way for the JWST: witnessing globular cluster formation at z > 3

We report on five compact, extremely young (<10Myr) and blue (\beta_UV<-2.5, F_\lambda =\lambda^\beta) objects observed with VLT/MUSE at redshift 3.1169, 3.235, in addition to three objects at z=6.145. These sources are magnified by the Hubble Frontier Field galaxy clusters MACS~J0416 and AS1063. Their de-lensed half light radii (Re) are between 16 to 140pc, the stellar masses are ~1-20 X 10^6 Msun, the magnitudes are m_uv=28.8 - 31.4 (-17<Muv<-15) and specific star formation rates can be as large as ~800Gyr^-1. Multiple images of these systems are widely separated in the sky (up to 50'') and individually magnified by factors 3-40. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-globular clusters (proto-GC) discovered so far. Rest-frame optical high dispersion spectroscopy of one of them at z=3.1169 yields a velocity dispersion \sigma_v~20km/s, implying a dynamical mass dominated by the stellar mass. Another object at z=6.145, with de-lensed Muv ~ -15.3 (m_uv ~ 31.4), shows a stellar mass and a star-formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z=6.145, with de-lensed m_uv ~ 32, a stellar mass of 0.5 X 10^6 Msun and a star formation rate of 0.06 Msun/yr is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z>3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the universe and augment Lya visibility during reionization. This work underlines the crucial role of JWST in characterizing the rest-frame optical and near-infrared properties of such low-luminosity high-z objects.

Characterizing dw1335-29, a recently discovered dwarf satellite of M83

The number, distribution, and properties of dwarf satellites are crucial probes of the physics of galaxy formation at low masses and the response of satellite galaxies to the tidal and gas dynamical effects of their more massive parent.To make progress, it is necessary to augment and solidify the census of dwarf satellites of galaxies outside the Local Group. M\"uller et al. (2015) presented 16 dwarf galaxy candidates near M83, but lacking reliable distances, it is unclear which candidates are M83 satellites. Using red giant branch stars from the HST/GHOSTS survey in conjunction with ground-based images from VLT/VIMOS, we confirm that one of the candidates, dw1335-29-- with a projected distance of 26 kpc from M83 and a distance modulus of $(m - M)_0 = 28.5^{+0.3}_{-0.1}$ -- is a satellite of M83. We estimate an absolute magnitude $M_V = -10.1 \pm{0.4}$, an ellipticity of $0.40^{+0.14}_{-0.22}$, a half light radius of $656^{+121}_{-170 }$ pc, and [Fe/H] = $-1.3^{+0.3}_{-0.4}$. Owing to dw1335-29's somewhat irregular shape and possible young stars, we classify this galaxy as a dwarf irregular or transition dwarf. This is curious, as with a projected distance of 26 kpc from M83, dw1335-29 is expected to lack recent star formation. Further study of M83's dwarf population will reveal if star formation in its satellites is commonplace (suggesting a lack of a hot gas envelope for M83 that would quench star formation) or rare (suggesting that dw1335-29 has a larger M83-centric distance, and is fortuitously projected to small radii).

A COMPARATIVE STUDY OF LONG AND SHORT GRBS. I. OVERLAPPING PROPERTIES

ABSTRACT Gamma-ray bursts (GRBs) are classified into long and short categories based on their durations. Broadband studies suggest that these two categories of objects roughly correspond to two different classes of progenitor systems, i.e., compact star mergers (Type I) versus massive star core collapse (Type II). However, the duration criterion sometimes leads to mis-identification of the progenitor systems. We perform a comprehensive multi-wavelength comparative study between duration-defined long GRBs and short GRBs as well as the so-called “consensus” long GRBs and short GRBs (which are believed to be more closely related to the two types of progenitor systems). The parameters we study include two parts: the prompt emission properties including duration (T 90), spectral peak energy ( ), low energy photon index (α), isotropic γ-ray energy ( ), isotropic peak luminosity ( ), and the amplitude parameters (f and ); and the host galaxy properties including stellar mass ( ), star formation rate, metallicity ([X/H]), half light radius (R 50), angular and physical ( ) offset of the afterglow from the center of the host galaxy, the normalized offset ( ), and the brightness fraction . For most parameters, we find interesting overlapping properties between the two populations in both one-dimensional (1D) and 2D distribution plots. The three best parameters for the purpose of classification are T 90, , and . However, no single parameter alone is good enough to place a particular burst into the right physical category, suggesting the need for multiple criteria for physical classification.