National Astronomy Meeting Poster Exhibition

The UV radiation is considered to be one of the best tracers of star formation rate (SFR), but it only gives an incomplete picture of the star formation activity. A big fraction of the UV emission produced by stars does not manage to escape the dust in the star forming regions. There are proposed methods to correct the star formation rate for the dust absorption. These relations, calibrated in the local universe and then applied to surveys at higher redshifts, are under the scanner recently.
The questions that arise now are : whether these relations evolve as we trace back the history of the universe? And whether (or not) these relations keep their functional form as the ensemble properties of galaxies change? In this work we try to answer these questions using UV data from XMM-Newton Optical/UV Monitor telescope (XMM-OM) and FIR data from the five Herschel bands. We stack the UV sources on the FIR maps from Herschel PACS and SPIRE instruments to produce average estimates of the FIR luminosities coming from the UV selected star-forming galaxies. The dust attenuation relation is constrained using the IRX ratio in the redshift range 0.6 - 1.2 which corresponding to the epoch just after the peak of the star formation activity in the universe.

A look at the Madau plot shows that the scatter in the star formation rate (SFR) density at redshift 4 is large. Upcoming facilities are expected will resolves this scatter. At lower redshift end of the peak of the SFR, we would expect a better situation, alas it is not. At redshift ~ 1 the scatter is as bad if not worse. GALEX and HST have been used in the past to get better constraints in this redshift regime. With its large FOV, GALEX provides a <br />good sky coverage, but because of its coarse PSF, source confusion becomes a big problem. HST on the other hand has amazing resolution, but the small area covered brings cosmic variance into picture.<br />The XMM-Newton Optical/UV Monitor telescope (XMM-OM) provides UV imaging with a nice compromise between the FOV and PSF. Now into its early twenties, XMM-Newton has a wealth of archival data waiting to be explored. In this work we use data collected over a time period of 10 years by XMM-OM. In particular we use the UVW1 (291 nm) imaging that covers 395 sq. arcmins of the CDFS down to UVW1 mag 24.5 and 1.56 sq. degrees of COSMOS field to a depth of 23.0 UVW1 magnitudes. Our calculations of the Galaxy luminosity function (LF) at rest frame 150 nm, show that the characteristic magnitude M* evolves significantly during this epoch, in contrast with the previous studies.<br />Using the UV LF we estimate the SFR density in the redshift range 0.6 to 1.2.

MHD plasma turbulence is believed to play a vital role in the production of energetic electrons during solar flares and the non-thermal broadening of spectral lines is a key sign of this turbulence. Here, we determine how flare turbulence evolves in time and in space using spectral profiles of Fe XXIV, Fe XXIII and Fe XVI, observed by Hinode/EIS. Maps of non-thermal velocity are created for times covering the X-ray rise, peak, and decay. We find that turbulence is not localised in the loop apex but distributed throughout the entire flare; often greatest in the coronal loop tops, and decaying at different rates at various locations in the flare. For hotter ions, the non-thermal velocity decreases as the flare evolves and after the X-ray peak it shows a clear spatial variation, decreasing linearly from the loop apex towards the ribbon. The non-thermal velocity of Fe XVI remains relativity constant throughout the flare, but steeply increases in one region corresponding to the southern ribbon, peaking just prior to the peak in HXRs before declining. The creation of kinetic energy density maps reveal where energy is available for electron energisation, suggesting that similar levels of kinetic energy may be available to both heat and/or energise electrons in large regions of the flare. These results are useful for constraining the spatial distribution of, and mechanisms that create, turbulence in flares.

Energetic electrons in the upper solar corona produce sources of radio emission observed at metric and deca-metric wavelengths. This emission provides unique diagnostic information about the characteristics of energetic electrons as well as the state of the coronal plasma. However, the sizes and shapes of these sources and their variation with frequency are not well understood. This is due to the relatively low spatial resolution and other effects, including ionospheric refraction and scattering.

We describe a novel empirical method for calibrating and interpreting solar imaging observations, accounting for instrumental and ionospheric effects. The method is based on observations of known compact radio sources in the same wavelength range. Using the developed method we derive the sizes and shapes of solar radio sources observed by the Low-Frequency Array (LOFAR) in the tied-array beam mode in the frequency range 30-45MHz. It is shown that in nine randomly selected events the source sizes range from about 3 to 20 arcminutes, and decrease with frequency. The corrected sizes and shapes of radio sources are in a good agreement with the results of numerical simulations of anisotropic radio-wave scattering in the solar corona.

We explore the Mass-Metallicity relation (MZR) for ~1000 nearby galaxies using integrated properties from the extended version of the CALIFA integral field spectroscopy data. We focused on exploring the best mathematical form that describes the observed MZR through different functional forms as well as different statistical environments. To test the goodness of the fit of the MZR, we identify the function that yields the smallest scatter in its residuals. We use this residual to explore possible secondary relations of the MZR with other observables (e.g., SFR, Gas mass, gas fraction, and morphology). Among other results, we note a significant lack of an anti-correlation between these residuals and the SFR, in contrast to previous studies. Our results suggest that the functional form and the presence of secondary relations may depend on statistical treatment.

The solar corona is shaped and mysteriously heated to millions of degrees by the Sun’s magnetic field. It has long been hypothesized that the heating results from a myriad of tiny magnetic energy outbursts called nanoflares, driven by the fundamental process of magnetic reconnection. Misaligned magnetic field lines can break and reconnect, producing nanoflares in avalanche-like processes. However, no direct and unique observations of such nanoflares exist to date, and the lack of a smoking gun has cast doubt on the possibility of solving the coronal heating problem. From coordinated multi-band high-resolution observations, we report on the discovery of very fast and bursty nanojets, the telltale signature of reconnection-based nanoflares resulting in coronal heating. The nanojet is uniquely characterised by being transverse to the loop and appears as a unidirectional jet from the reconnection point. Isolated and clustered nanojets are detected, and a myriad are observed in an avalanche-like progression, leading to the formation of a coronal loop. Using state-of-the-art numerical simulations, we demonstrate that the nanojet is a consequence of the slingshot effect from the magnetically tensed, curved magnetic field lines reconnecting at small angles. Nanojets are therefore the key signature of reconnection-based coronal heating in action.

We present a new set of measurement of [alpha/Fe] for galaxies in the SAMI galaxy survey. We show that an increase in [alpha/Fe] in high-density environments (HDEs) is not driven by an increase in the red fraction of galaxies. The alpha-enhancement is morphology dependent, being strongest in ellipticals, and occurs primarily at low velocity dispersions (200km/s), we find no difference in the [alpha/Fe] ratio of galaxies, and hence infer that the integrated star-formation timescales cannot differ substantially between high-sigma galaxies across varied environments.
We also present an analysis comparing the residual dependence of [alpha/Fe] against the kinematic properties of the sample, primarily against the spin proxy, lambda_R. We show that for a spectroscopically selected quenched subsample, the intrinsic spin of a galaxy appears to have no relation to the duration of star formation prior to quenching.

The reaction network in the neutron-deficient part of the nuclear chart around A~ 100 contains several nuclei of importance to astrophysical processes, such as the p-process. This work reports on the results from recent experimental studies of the radiative proton-capture reactions 112,114Cd(p,γ)113,115In. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched 112Cd and 114Cd targets. Two different techniques, in-beam γ-ray spectroscopy and the activation method have been implemented, were the latter is considered mandatory to account for the presence of low-lying isomers in 113In (E≈392 keV, t1/2≈100 min), and 115In (E≈336 keV, t1/2≈4.5 h). Following the measurement of the cross sections, the astrophysical S factors have been subsequently deduced. The experimental results are compared to detailed Hauser-Feshbach theoretical calculations carried out with TALYS v1.95

The ExoMars Rover, launching in 2022, is designed to search for signs of past life through surface, sub-surface and atmospheric measurements using a wide array of instruments. One of them is the multispectral stereo imager, PanCam, containing a pair of Wide Angle Cameras (WACs), each with an 11-position filter wheel, and a High Resolution Camera (HRC). Two solar filters, SO1 and SO2, centered at 925nm and 935nm can be utilised to measure water vapour content in the atmosphere by measuring the 936 nm absorption feature. Through direct imaging of the rising and setting Sun as well as imaging the scattered light at the horizon, vertical distribution of water vapour can be retrieved in the lower Martian atmosphere. Using radiative transfer techniques and a sophisticated retrieval tool, NEMESIS (Non-linear optimal Estimator for MultivariatE Spectral analysIS), a vertical height profile can be computed. Currently, we are investigating the accuracy of these measurements using a PanCam instrument model and the Planetary Spectrum Generator tool. We are also investigating if similar measurements of water vapour in the lower atmosphere can be carried out using the MastCam-Z instrument onboard the Perseverance Rover at Jezero Crater.

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