2009 (IPP)

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21-cm absorbers at intermediate redshifts
(2009-02-01) Gupta, N.; Srianand, R.; Petitjean, Patrick; et al.
Damped Lyman-α systems (DLAs) seen in the spectra of high-z QSOs allow us to probe the physical conditions in protogalaxies. Our understanding of physical conditions in DLAs at high-z is primarily based on the absorption lines of H2 molecules and ﬁne-structure transitions. Another important way of probing the thermal state of interstellar medium in these systems is by studying the 21-cm absorption in the spectra of background quasars. Here we report the main results of our GMRT survey to search for 21-cm absorption in a representative and unbiased sample of 35 DLA candidates at 1.10≤z≤1.45. Our sample of DLA candidates is drawn from the strong Mg ii systems in SDSS DR5 and has resulted in discovery of 9 new 21-cm absorbers. Prior to our survey only one 21-cm absorber was known in the redshift range: 0.7≤z≤2. This survey has allowed us to investigate the dependence of detectability of 21-cm absorption on the properties of UV absorption lines detected in SDSS spectra and estimate the number per unit redshift of 21-cm absorbers. Our GMRT survey provides a representative sample of systems that can be used in combination with various follow-up observations: (1) for investigating the physical conditions in the absorbing gas using spin temperature (TS) measurements, (2) for investigating the eﬀect of metallicity and dust content on the detectability of 21-cm absorption, (3) for studying the morphology of the absorbing gas and (4) for probing the time evolution of various fundamental constants. Results from the ﬁrst phase of our survey are presented in Gupta et al. (2007). Detailed description of the entire sample and results from the survey are presented in Gupta et al. (2009).
Automated star-galaxy segregation using spectral and integrated band data for TAUVEX/ASTROSAT satellite data pipeline
(2009-04-01) Bora, Archana; Harinder, P.; Gupta, Ranjan; et al.
We employ an Artiﬁcial Neural Network (ANN) based technique to develop a pipeline for automated segregation of stars from the galaxies to be observed by Tel-Aviv University Ultra-Violet Experiment (TAUVEX). We use synthetic spectra of stars from UVBLUE library and selected International Ultraviolet Explorer (IUE) low resolution spectra for galaxies in the ultraviolet (UV) region from 1250 to 3220Å as the training set and IUE low-resolution spectra for both the stars and the galaxies as the test set. All the data sets have been pre-processed to get band integrated ﬂuxes so as to mimic the observations of the TAUVEX UV imager. We also perform the ANN based segregation scheme using the full length spectral features (which will also be useful for the ASTROSAT mission). Our results suggest that, in the case of the non-availability of full spectral features, the limited band integrated features can be used to segregate the two classes of objects; although the band data classiﬁcation is less accurate than the full spectral data classiﬁcation.
Bipolar Harmonic encoding of CMB correlation patterns
(2009-12-01) Joshi, Nidhi; Jhingan, S.; Souradeep, Tarun; et al.
Deviations from statistical isotropy can be modeled in various ways, for instance, anisotropic cosmological models (Bianchi models), compact topologies and presence of primordial magnetic ﬁeld. Signature of anisotropy manifests itself in CMB correlation patterns. Here we explore the symmetries of the correlation function and its implications on the observable measures constructed within the Bipolar harmonic formalism for these variety of models. Diﬀerent quantiﬁers within the Bipolar harmonic representation are used to distinguish between plausible models of breakdown of statistical isotropy and as a spectroscopic tool for discriminating between distinct cosmic topology.
CMB Polarization and Temperature Power Spectra Estimation using Linear Combination of WMAP 5-year Maps
(2009-03-01) Souradeep, Tarun; Jain, Pankaj; Saha, Rajib; et al.
We estimate CMB polarization and temperature power spectra using WMAP 5-year foreground contaminated maps. The power spectrum is estimated by using a model independent method, which does not utilize directly the diﬀuse foreground templates nor the detec tor noise model. The method essentially consists of two steps, (i) removal of diﬀuse foregrounds contamination by making linear combination of individual maps in harmonic space and (ii) cross-correlation of foreground cleaned maps to minimize detector noise bias. For temperature power spectrum we also estimate and subtract residual unre- solved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our 1TT, TE and EE power spectra are in good agreement with the published results of the WMAP science team. The error bars on the polarization power spectra, however, turn out to be smaller in comparison to what is obtained by the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We ﬁnd that the bias is small in all cases. A negative bias at low l in TT power spectrum has been pointed in an earlier publication. We ﬁnd that the bias corrected quadrupole power (l(l + 1)Cl/2π) is 532 µK2, approximately 2.5 times the estimate (213.4 µK2) made by the WMAP team.
Complete sample of 21-cm absorbers at z ~ 1.3: Giant Metrewave Radio Telescope Survey Using Mg II Systems
(2009-04-01) Gupta, N.; Srianand, R.; Petitjean, Patrick; et al.
We present the results of a systematic Giant Metrewave Radio Telescope (GMRT) survey of 21-cm absorption in a representative and unbiased sample of 35 strong Mg ii systems in the redshift range: zabs∼1.10−1.45, 33 of which have Wr ≥1˚ A. The survey using ∼400 hrs of telescope time has resulted in 9 new 21-cm detections and stringent 21-cm optical depth upper limits (median 3σ optical depth per 10 kms−1 of 0.017) for the remaining 26 systems. This is by far the largest number of 21-cm detections from any single survey of intervening absorbers. Prior to our survey no intervening 21-cm system was known in the above redshift range and only one system was known in the redshift range 0.7 ≤ z ≤ 1.5. We discuss the relation between the detectability of 21-cm absorption and various properties of UV absorption lines. We show that if Mg ii systems are selected with the following criteria, Mg ii doublet ratio ≤1.3 and Wr(Mg i)/Wr(Mg ii) ≥ 0.3, then a detection rate of 21-cm absorption up to 90% can be achieved. We estimate n21, the number per unit redshift of 21-cm absorbers with Wr(Mg ii) > Wo and integrated optical depth T21 > To and show that n21 decreases with increasing redshift. In particular, for Wo = 1.0 ˚ A and To > 0.3 km s−1, n21 falls by a factor 4 from < z > = 0.5 to < z > = 1.3. The evolution seems to be stronger for stronger Mg ii systems. Using a subsample of systems for which high frequency VLBA images are available, we show that the eﬀect is not related to the structure of the background radio sources and is most probably due to the evolution of the cold neutral medium ﬁlling factor in Mg ii systems. We ﬁnd no correlation between the velocity spread of the 21-cm absorption feature and Wr(Mg ii) at z ∼ 1.3
Constraining fundamental constants of physics with quasar absorption line systems
(2009-08-01) Petitjean, Patrick; Vivek, M.; Mohan, V.; et al.
We report long-slit spectroscopic observations of SDSS J092712+294344 carried-out at the recently commissioned 2m telescope in IUCAA Girawali Observatory, India. This AGN-like source is known to feature three sets of emission lines at zem = 0.6972, 0.7020 and 0.7128. Diﬀerent scenarios such as a recoiling black hole after asymmetric emission of gravitational waves, binary black holes and possible merging systems are proposed for this object. We test these scenarios by comparing our spectra with that fromthe Sloan Digital Sky Survey (SDSS), obtained 4 years prior to our observations. Comparing the redshifts of [Oiii]λλ4960,5008 we put a 3σ limit on the relative acceleration to be less than 32 km s−1 yr −1 between diﬀerent emitting regions. Using the 2D spectra obtained at diﬀerent position angles we show that the [Oiii]λ5008 line from the zem = 0.7128 component is extended beyond the spectral point spread function.We infer the linear extent of this line emitting region is ∼ 8 kpc.We also ﬁnd a tentative evidence for an oﬀset between the centroid of the [Oiii]λ5008 line at zem = 0.7128 and the QSO trace when the slit is aligned at a position angle of 299◦ . This corresponds to the zem = 0.7128 system being at an impact parameter of ∼1 kpc with respect to the zem = 0.6972 in the north west direction. Based on our observations we conclude that the binary black hole model is most unlikely. The spatial extent and the sizes are consistent with both black hole recoil and merging scenarios
Detecting gravitational waves from inspiraling binaries with a network of geographically separated detectors: coherent versus coincident strategies
(2009-10-01) Mukhopadhyay, Himan; Tagoshi, H.; Dhurandhar, Sanjeev; et al.
We compare two strategies of multi-detector detection of compact binary inspiral signals, namely, the coincidence and the coherent for the realistic case of geographically separated detectors. The naive coincident strategy treats the detectors as if they are isolated - compares individual detector statistics with their respective thresholds while the coherent strategy combines the detector network data coherently to obtain a single detection statistic which is then compared with a single threshold. We also consider an enhanced coincidence strategy which is intermediate in the sense that though the individual statistics are added in quadrature and the sum compared with a single threshold, the estimated parameters are also checked for consistency. For simplicity, we consider detector pairs having the same power spectral density of noise, as that of initial LIGO and also assume the noise to be stationary and Gaussian. Further, since we consider the detectors to be widely separated on Earth, we take the instrumental noises to be uncorrelated; the wide separation implicitly means that since the detector arms must lie parallel to the Earth’s surface, the detectors necessarily have diﬀerent orientations. We compare the performances of the methods by plotting the receiver operating characteristics (ROC) for the strategies. Several results are derived analytically in order to gain insight. Simulations are performed in order to plot the ROC curves. A single astrophysical source as well as a distribution of sources is considered. We assume one year data train and a mass range of 1 − 40M⊙ for the case of astrophysically distributed sources. We ﬁnd that the coherent strategy is superior to the two coincident strategies that we consider. Remarkably, the detection probability of the coherent strategy is 50% better than the naive coincident strategy. One the other hand, diﬀerence in performance between the coherent strategy and enhanced coincident strategy is not very large. Even in this situation, it is not diﬃcult to perform the real data analysis with the coherent strategy. The bottom line is that the coherent strategy is a good detection strategy.
Diffuse molecular gas at high redshift: Detection of CO molecules and the 2175 A* dust feature at z=1.64
(2009-06-01) Noterdaeme, P.; Ledoux, C.; Srianand, R.; et al.
We present the detection of carbon monoxide molecules (CO) at z = 1.6408 towards the quasar SDSS J160457.50+220300.5 using the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph. CO absorption is detected in at least two components in the ﬁrst six A-X bands and one d-X(5-0) inter-band system. This is the second detection of this kind along a quasar line of sight. The CO absorption proﬁles are well modelled assuming a rotational excitation of CO in the range 6 < Tex < 16 K, which is consistent with or higher than the temperature of the Cosmic Microwave Background Radiation at this redshift. We derive a total CO column density of N(CO) = 4 × 1014 cm−2 . The measured column densities of S i, Mg i, Zn ii, Fe ii and Si ii indicate a dust depletion pattern typical of cold gas in the Galactic disc. The background quasar spectrum is signiﬁcantly reddened (u−K ∼ 4.5 mag) and presents a pronounced 2175 Å dust absorption feature at the redshift of the CO absorber. Using a control sample of ∼500 quasars we ﬁnd the chance probability for this feature to be spurious is ∼0.3%. We show that the spectral energy distribution (SED) of the quasar is well ﬁtted with a QSO composite spectrum reddened with a Large Magellanic Cloud supershell extinction law at the redshift of the absorber. It is noticeable that this quasar is absent from the colour-selected SDSS quasar sample. This demonstrates our current view of the Universe may be biased against dusty sightlines. These direct observations of carbonaceous molecules and dust open up the possibility of studying physical co
Magnetic quenching of alpha and diffusity tensors in helical turbulence
(2011-07-06) Brandenburg, Axel; Biman, B.; Subramanian, Kandaswamy; et al.
We study the implications of primordial magnetic ﬁelds for the thermal and ionization history of the post-recombination era. In particular we compute the eﬀects of dissipation of primordial magnetic ﬁelds owing to ambipolar diﬀusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing halos and compute the eﬀects of the altered thermal and ionization history on the formation of molecular hydrogen.We show that, for magnetic ﬁeld strengths in the range 2×10−10 G < ∼ B0 < ∼ 2× 10−9 G, the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor 5 to 1000 over the case with no magnetic ﬁelds. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of UV photons and the formation of ﬁrst structures in the universe
Metal-Enriched Plasma in Protogalactic Halos: A Survey of N V Absorption in High-z Damped & Sub-Damped Lyman-alpha Systems
(2009-01-01) Andrew, Fox; Prochaska, Jason X.; Ledoux, C´edric; et al.
We continue our recent work to characterize the plasma content of high-redshift damped and sub-damped Lyman-α systems (DLAs/sub-DLAs), which represent multi-phase gaseous (proto)galactic disks and halos seen toward a background source. We survey Nv absorption in a sample of 91 DLAs and 18 sub-DLAs in the redshift range 1.67−2.3. The Nv and Civ component b-value distributions in DLAs are statistically similar, but the median b(Nv) of 18 kms −1 is narrower than the median b(Ovi) of ≈25 kms −1 . Some ≈20% of the Nv components have b<10 kms −1 and thus arise in warm, photoionized plasma at log (T/K)<4.92; local sources of ionizing radiation (as opposed to the extragalactic background) are required to keep the cloud sizes physically reasonable. The nature of the remaining ≈80% of (broad) Nv components is unclear; models of radiatively-cooling collisionally-ionized plasma at log (T/K)=5.2–5.4 are fairly successful in reproducing the observed integrated high-ion column density ratios and the component line widths, but we cannot rule out photoionization by local sources. Finally, we identify several unusual DLAs with extremely low metallicity (<0.01 solar) but strong high-ion absorption [logN(Nv)>14 or logN(Ovi)>14.2], which present challenges to either galactic inﬂow or outﬂow models.
Model Independent Foreground Power Spectrum Estimation using WMAP 5-year Data
(2009-01-01) Ghosh, Tuhin; Saha, Rajib; Jain, Pankaj; et al.
In this paper, we propose & implement on WMAP 5-year data, a model independent approach of foreground power spectrum estimation for multifrequency observations of CMB experiments. Recently a model independent approach of CMB power spectrum estimation was proposed by Saha et al. 2006. This methodology demonstrates that CMB power spectrum can be reliably estimated solely from WMAP data without assuming any template models for the foreground components. In the current paper, we extend this work to estimate the galactic foreground power spectrum using the WMAP 5 year maps following a self contained analysis. We apply the model independent method in harmonic basis to estimate the foreground power spectrum and frequency dependence of combined foregrounds. We also study the behaviour of synchrotron spectral index variation over diﬀerent regions of the sky. We compare our results with those obtained from MEM foreground maps which are formed in pixel space. We ﬁnd that relative to our model independent estimates MEM maps overestimates the foreground power close to galactic plane and underestimates it at high latitudes.
Multi-wavelength observations of afterglow of GRB080319B and the modeling constraints
(2009-04-01) Pandey, S.B.; Castro-Tirado, A. J.; Jelinek, M.; et al.
Context. We present observations of the afterglow of GRB 080319B at optical, mm and radio frequencies from a few hours to 67 days after the burst. Aims. To understand the nature of this brightest explosion based on the observed properties and it’s comparison with the afterglow models. Methods. Present observations along with other published multi-wavelength data have been used to study the light-curves and spectral energy distributions of the burst afterglow. Results. Our results show that the observed features of the afterglow ﬁts equally good with the Inter Stellar Matter and the Stellar Wind density proﬁles of the circum-burst medium. In case of both density proﬁles, location of the maximum synchrotron frequency νm is below optical and the value of cooling break frequency νc is below X−rays, ∼ 104 s after the burst. Also, the derived value of the Lorentz factor at the time of naked eye brightness is ∼ 300 with the corresponding blast wave size of ∼ 1018 cm. Conclusions. The numerical ﬁt to the multi-wavelength afterglow data constraints the values of physical parameters and the emission mechanism of the burst.
On distribution of CMEs speed in solar cycle 23
(2009-02-01) Mittal, Nishant; Sharma, Joginder; Tomar, Vivek; et al.
We have analyzed the data for more than 12900 CMEs which were obtained by SOHO/LASCO during the period of 1996-2007. The online CME catalogue contains all major CMEs detected by LASCO C2 and C3 coronagraphs. Basically we determine the CME speeds from the linear and quadratic fits to the height-time measurements. It is found that linear (constant speed) fit is preferable for 90% of the CMEs. The distribution of speeds of CMEs in solar cycle 23 is presented along with those obtained by others. As expected, the speeds decrease in the decay phase of the cycle 23. There is an unusual drop in speed in the year 2001 and an abnormal increase in speed in the year 2003 due to the high concentration of CMEs, X-class soft X-ray flares, solar energetic particle (SEP) events and interplanetary shocks observed during October-November period called Halloween events.
Optical identification of XMM sources in the CFHTLS
(2009-05-01) Stalin, C. S.; Petitjean, Patrick; Srianand, R.; et al.
We summarize the attempts by our group and others to derive constraints on variations of fundamental constants over cosmic time using quasar absorption lines. Most upper limits reside in the range 0.5 1.5 10 5 at the 3 level over a redshift range of approximately 0:5 2:5 for the ﬁne-structure constant, , the proton-to-electron mass ratio, and a combination of the proton gyromagnetic factor and the two previous constants, gp( 2= ) , for only one claimed variation of . It is therefore very important to perform new measurements to improve the sensitivity of the numerous methods to at least <0.1 10 5 which should be possible in the next few years. Future instrumentations on ELTs in the optical and/or ALMA, EVLA and SKA pathﬁnders in the radio will undoutedly boost this ﬁeld by allowing to reach much better signal-to-noise ratios at higher spectral resolution and to perform measurements on molecules in the ISM of high redshift galaxi
Primordial magnetic fields and formation of molecular hydrogen
(2009-04-01) Sethi, Shiv K.; Nath, B. B.; Subramanian, Kandaswamy; et al.
We study the implications of primordial magnetic ﬁelds for the thermal and ionization history of the post-recombination era. In particular we compute the eﬀects of dissi- pation of primordial magnetic ﬁelds owing to ambipolar diﬀusion and decaying tur- bulence in the intergalactic medium (IGM) and the collapsing halos and compute the eﬀects of the altered thermal and ionization history on the formation of molecular hy- drogen.We show that, for magnetic ﬁeld strengths in the range 2×10−10 G < ∼ B0 < ∼ 2× 10−9 G, the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor 5 to 1000 over the case with no magnetic ﬁelds. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of UV photons and the formation of ﬁrst structures in the universe
Quasars probing intermediate redshift star-forming galaxies
(2009-12-01) Noterdaeme, P.; Srianand, R.; Mohan, V.; et al.
We present a sample of 46 [Oiii]-emitting galaxies at z < 0.8 detected in the ﬁbre spectra of quasars from the Sloan Digital Sky Survey, Data Release 7 (SDSS-DR7) through an automatic search procedure. We also detect [Oii] and Hβ emission lines from most of these galaxies in the SDSS spectra. We study both the emission and absorption properties of a sub sample of 17 galaxies in the redshift range z = 0.4-0.7, where Mg ii lines are covered by the SDSS spectra. The measured lower-limits on the star-formation rates of these galaxies are in the range 0.2-20 M⊙ yr −1 . The emission line luminosities and (O/H) metallicities from R23 measured in this sample are similar to what is found in normal galaxies at these redshifts. Thus, this constitutes a unique sample of intermediate redshift star-forming galaxies where we can study the QSO absorber - galaxy connection. Strong Mg ii (Wλ2796> ∼ 1 Å) as well as Mg i absorption lines are detected in the QSO spectra at the redshift of most of these galaxies. Strong Fe ii (Wλ2600 > 1 Å) absorption lines are also generally detected whenever the appropriate wavelength ranges are covered. This suggests that most of these systems could be bona-ﬁde Damped Lyman-α systems. We investigate various possible relations between the Mg ii rest equivalent widths and the emission line properties.We ﬁnd a possible (2σ) correlation between the emission-line metallicity of the galaxies and the Mg ii rest equivalent width of the absorbers (log(O/H) + 12 = 0.1Wλ2796 + 8.27), which could be a consequence of an underlying mass-metallicity relation. However, [Oiii]-selected Mg ii systems represent only a minor fraction of the strongMg ii absorbers.We ﬁnd this cannot be attributed to biases related either to the spectral signal-to-noise ratio or to the brightness of the QSOs. We measure the average observed ﬂuxes (collected into the SDSS ﬁbre) of the [Oii] and [Oiii] lines associated to Mg ii-selected systems through stacking technique.We ﬁnd that the average lumiosities of emission lines are higher for systems with larger Wλ2796. The stacked luminosities are found to be below the typical detection limit in individual spectra, indicating that faint galaxies can contribute appreciably to the observed population of strong Mg ii absorbers at intermediate redshifts.We also present long-slit spectroscopic observations of SDSS J113108+202151, the most luminous line-emitting galaxy in our z ≥ 0.4 sample. Surprisingly, we ﬁnd that the line-emitting region does not coincide with the nearby extended bright galaxy with consistent photometric redshift seen in the SDSS image.
Radio observations of ZwCl 2341.1+0000: a double radio relic cluster
(2009-10-01) Weeren, R.; Miniati, F.; Bagchi, Joydeep; et al.
infall and mergers of smaller subclusters and galaxy groups. Diﬀuse radio emission, in the form of radio halos and relics, is found in clusters undergoing a merger, indicating that shocks or turbulence associated with the merger are capable of accelerating electrons to highly relativistic energies. Double relics are a rare class of radio sources found in the periphery of clusters, with the two components located symmetrically on the opposite sides of the cluster center. These relics are important probes of the cluster periphery as (i) they provide an estimate of the magnetic ﬁeld strength, and (ii) together with detailed modeling can be used to derive information about the merger geometry, mass, and timescale. Observations of these double relics can thus be used to test the framework of LSS formation. Here we report on radio observations of ZwCl 2341.1+0000, a complex merging structure of galaxies located at z = 0.27, using Giant Metrewave Radio Telescope (GMRT) observations. Aims. The main aim of the observations is to study the nature of the diﬀuse radio emission in the galaxy cluster ZwCl 2341.1+0000. Methods. We carried out GMRT 610, 241, and 157 MHz continuum observations of ZwCl 2341.1+0000. The radio observations are combined with X-ray and optical data of the cluster. Results. The GMRT observations show a double peripheral radio relic in the cluster ZwCl 2341.1+0000. The spectral index is −0.49 ± 0.18 for the northern relic and −0.76 ± 0.17 for the southern relic. We have derived values of 0.48 − 0.93 µGauss for the equipartition magnetic ﬁeld strength. The relics are probably associated with outward traveling merger shock waves.
Reconnecting Flux Rope Dynamo
(2009-10-01) Subramanian, Kandaswamy; Baggaley, Andrew W; Barenghi, Carlo F.; et al.
We develop a new model of the ﬂuctuation dynamo in which the magnetic ﬁeld is conﬁned to thin ﬂux ropes advected by a multi-scale model of turbulence. Magnetic dissipation occurs only via reconnection of the ﬂux ropes. This model can be viewed as an implementation of the asymptotic limit Rm → ∞ for a continuous magnetic ﬁeld, where magnetic dissipation is strongly localized to small regions of strong ﬁeld gradients. We investigate the kinetic energy release into heat, mediated by the dynamo action, both in our model and by solving the induction equation with the same ﬂow. We ﬁnd that a ﬂux rope dynamo is an order of magnitude more eﬃcient at converting mechanical energy into heat. The probability density of the magnetic energy release in reconnections has a power-law form with the slope −3, consistent with the Solar corona heating by nanoﬂares.
SDSS J092712.64+294344.0: recoiling black hole or merging galaxies
(2009-08-01) Vivek, M.; Srianand, R.; Noterdaeme, P.; et al.
We report long-slit spectroscopic observations of SDSS J092712+294344 carried-out at the recently commissioned 2m telescope in IUCAA Girawali Observatory, India. This AGN-like source is known to feature three sets of emission lines at zem = 0.6972, 0.7020 and 0.7128. Diﬀerent scenarios such as a recoiling black hole after asymmetric emission of gravitational waves, binary black holes and possible merging systems are proposed for this object. We test these scenarios by comparing our spectra with that fromthe Sloan Digital Sky Survey (SDSS), obtained 4 years prior to our observations. Comparing the redshifts of [Oiii]λλ4960,5008 we put a 3σ limit on the relative acceleration to be less than 32 km s−1 yr −1 between diﬀerent emitting regions. Using the 2D spectra obtained at diﬀerent position angles we show that the [Oiii]λ5008 line from the zem = 0.7128 component is extended beyond the spectral point spread function.We infer the linear extent of this line emitting region is ∼ 8 kpc.We also ﬁnd a tentative evidence for an oﬀset between the centroid of the [Oiii]λ5008 line at zem = 0.7128 and the QSO trace when the slit is aligned at a position angle of 299◦ . This corresponds to the zem = 0.7128 system being at an impact parameter of ∼1 kpc with respect to the zem = 0.6972 in the north west direction. Based on our observations we conclude that the binary black hole model is most unlikely. The spatial extent and
TELICS-A Telescope Instrument Control System for Small/Medium Sized Astronomical Observatories
(2009-10-01) Srivastava, Mudit K.; Ramaprakash, A. N.; Burse, Mahesh P.; et al.
For any modem astronomical observatory, it is essential to have an efficient interface between the telescope and its back-end instruments. However, for small and medium-sized observatories, this requirement is often limited by tight financial constraints. Therefore a simple yet versatile and low-cost control system is required for such observatories to minimize cost and effort. Here we report the development of a modem, multipurpose instrument control system TELlCS (Telescope Instrument Control System) to integrate the controls of various instruments and devices mounted on the telescope. TELlCS consists of an embedded hardware unit known as a common control unit (CCU) in combination with Linux-based data acquisition and user interface. The hardware of the CCU is built around the ATmega 128 microcontroller (Atmel Corp.) and is designed with a backplane, master-slave architecture, A Qt-based graphical user interface (GUI) has been developed and the back-end application software is based on C/C++. TELlCS provides feedback mechanisms that give the operator good visibility and a quick-look display of the status and modes of instruments as well as data. TELICS has been used for regular science observations since 2008 March on the 2 m, fllO IUCAA Telescope located at Girawali in Pune, India.