Multiwavelength Astronomy: Tool To Probe The Universe

Abstract

It is impossible to study all astronomical objects at a time, that is why one of the main task of astronomers is to search and find those particular objects that will provide a lot of understanding of the physics of objects and phenomena. In last few decades it is observed that we could see the universe in only one window that is optical. But now a day due to modern observing facility we can see the universe throughout all the wavelengths of electromagnetic spectrum. In this paper we are going to discuss astronomical data archives and data analysis tools to probe the universe in all wavelengths .This task are being achieved by astronomical surveys; having observed large areas of the sky, one can select interesting objects by definite criteria. Surveys are the backbones of astronomy, and therefore the engine of discovery. They’re of cultural importance, as a result of this they satisfy the need to map our surroundings, and provide a sense for wherever we tend to live.

Introduction

The major characteristic of modern astronomy is to study multiwavelength (MW) (from γ-ray to radio) and big data (data acquisition, storage and analysis). Now a day astronomical databases and archives contain billions of objects observed at different wavelengths, both galactic and extragalactic, and the vast amount of data on them allows new studies and discoveries [1]. Radiations coming from astronomical objects are the only tool to study them, and it is found that astronomical object emits all wavelengths in electromagnetic spectrum from radio waves to gamma rays. Emission of Radio waves having temperature less than 10 K are coming from cosmic background radiation ,scattering of free electrons in interstellar plasmas, cold gas and dust between the stars, regions near white dwarfs and neutron stars, supernova remnants, dense regions of interstellar space such as the galactic center, cold molecular clouds. Microwaves having temperature same as that of radio waves shows background radiation of the universe (remnant of

Big Bang). Infrared have the temperature 10 – 10 3 K comes from cool stars, star-forming regions, interstellar dust warmed by starlight, planets, comets and asteroids. as per as visible light is concerned 10 3 – 10 4 K Planets, Stars ,Galaxies, Nebulae. Ultraviolet radiation comes from Supernova remnants ,very hot star, quasars and has temperature range 10 4 – 10 6 K. X-rays are high energetic radiations with temperature 10 6 – 10 8 K and they emits from regions of hot, shocked gas, gas in clusters of galaxies, neutron stars ,supernova remnants, and the hot outer layers of stars. Finally gamma ray emission takes place from interstellar clouds where cosmic rays collide with hydrogen nuclei , disks of material surrounding black holes, pulsars or neutron stars , gamma rays has highest energy with temperature more than 108K.

Data Acquisition

Multiwavelength data can be acquired from different arxives some of them discussed here

1. Nasa Extragalactic Database (NED)

It is one of the a comprehensive database of multiwavelength data for extragalactic objects, providing a scientific and systematic information of hundreds of large sky surveys and thousands of research articles. It gives information of entire electromagnetic spectrum from gamma rays to radio waves. As new observations are added through publications, they are cross-identified or statistically related with previous data and integrated into a unified database to simplify queries and retrieval. It has connectivity with the NASA astrophysics mission archives (MAST, HEASARC, and IRSA) to the astrophysics literature via ADS, and to other data centers around the world. The database additionally includes a master index of various astrophysical objects, associations, positions, redshifts, spectra, redshift-independent distances, images, photometry, diameters, and elaborate notes. With this it gives information regarding derived quantities which includes Galactic extinction, velocity corrections, quick-look luminosities ,Hubble flow distances and scales, cosmological corrections and spectral energy distributions (SEDs). Objects information can be found by name, near name or near position and references can be queried by author and by object name.

2. High Energy Astrophysics Science Archive Research Center(HEASARCH):

HEASARC is the High energy archive for NASA’s missions studying electromagnetic radiation from extremely energetic cosmic phenomena ranging from black holes to the Big Bang. Since its merger with the Legacy Archive for Microwave Background Data Analysis (LAMBDA) in 2008, the HEASARC archive contains data obtained by high-energy astronomy missions observing in the extreme-ultraviolet (EUV), X-ray, and gamma-ray bands, as well as data from space missions, balloons, and ground-based facilities that have studied the relic cosmic microwave background (CMB) radiation in the sub-mm, mm and cm bands.

3. Chandra Data Archive (CDA)

The Chandra Data Archive (CDA) plays a central role in the operation of the Chandra X-ray Center (CXC) by providing support to the astronomical community in accessing Chandra data. The CDA offers access to digital archives through powerful query engines, including VO-compliant interfaces and also serves as a permanent storage repository of contributed data products by authors who have processed images or other pertinent and valuable datasets that are essential to their publications. We can access the Chandra Data Archive through ChaSeR: Search & Retrieval interface for scientists, allowing specification of detailed selection criteria. Chandra Fast Image is a simplified quick search tool for Chandra X-ray images and other data for the general public and FTP: Direct FTP access to the primary and secondary data products for all observations that are publicly released.

4. Hubble Legacy Archive (HLA)

HLA is indented to optimize science from the Hubble Space Telescope (HST) by providing data in the infrared, visible and ultraviolet. .The HLA is a joint project of the Space Telescope European Coordinating Facility (ST-ECF), Space Telescope Science Institute (STScI), and the Canadian Astronomy Data Centre (CADC).

The goal of the HLA is to provide high level products, online for immediate access, data quality data discovery and system properties[2].

5. NASA/IPAC Infrared Science Archive (IRSA)

IRSA is dedicated to serve calibrated science products from NASA's infrared and sub millimeter missions, together with 2MASS, IRAS, ISO, SWAS and MSX surveys, observatory missions. IRSA provides online and machine-friendly tools for efficient access to these data sets.

To know additional about what data are available through IRSA, view following lists of IRSA's holdings divided into catalogs, images, and spectra.

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• COSMOS Evolution Survey
• ISO Infrared Space Observatory
• Spitzer Space Telescope
• IRAS Infrared Astronomical Satellite
• 2MASS Two Micron All Sky Survey
• IRTS Infrared Telescope in Space
• WISE Wide-field Infrared Survey
• Herschel Space Observatory
• SWAS Sub millimeter Wave Astronomy Satellite
• AND others like BLAST, BOLOCAM, MSX, PTF

6. Very Large Array (VLA)

Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory situated at central New Mexico on the Plains of San Agustin, between the cities of Magdalena and Datil at about (80 km) west of Socorro. The VLA contains twenty-seven 25-meter radio telescopes deployed in a Y-shaped array and all the equipment, instrumentation, and computing power to function as an interferometer. Over the last 20 years, the VLA has proved to be one of the most successful and widely used radio telescopes. The Expanded Very Large Array (EVLA) is a technical upgrade using the same antennas with a new receiving system that covers the entire frequency range 1-50 GHz in ten bands [3].Astronomers using the VLA takes observations of black holes and protoplanetary disks around young stars, finded magnetic filaments and traced complex gas motions at the Milky Way's center and provided new knowledge about the physical mechanisms that produce radio emission.

7. Giant Metrewave Radio Telescope (GMRT):

National Center for Radio Astronomy (NCRA) is unique facility for radio astronomical research using the metrewavelengths range of the radio spectrum, known as the Giant Metrewave Radio Telescope (GMRT), it is located near Pune at a distance of about 80 km. GMRT consists of 30 fully steerable gigantic parabolic dishes of 45m diameter and it is spread over distances of up to 25 km [4]. The GMRT is designed to operate at six frequencies 50MHz, 150MHz, 235MHz, 325MHz, 610MHz and 1000-1450MHz.

8.ASTROSAT

AstroSat is a India’s first space observatory, was launched in 2015 and it is multi wavelength space observatory which observes universe in the optical, ultraviolet, low and high energy X-ray regions of the spectrum[5]. Whereas most other scientific satellites are capable of observing a narrow range of wavelength band. All major astronomy Institutions throughout the world and some Universities in India are participating in these observations. It has five major instruments with totally different objectives.

• i) The Ultraviolet Imaging Telescope (UVIT): It is constructed for observing the sky in the Visible, Near Ultraviolet (NUV) and Far Ultraviolet (FUV) regions of the electromagnetic spectrum
• ii) Large Area X-ray Proportional Counter (LAXPC): It is designed to study the variations in the emission of X-rays from sources like, Active Galactic Nuclei (AGN) ,X-ray binaries and other cosmic sources.
• iii) Soft X-ray Telescope (SXT) is designed for studying how the X-ray spectrum of 0.3-8 keV range coming from distant celestial bodies varies with time.
• iv) Cadmium Zinc Telluride Imager (CZTI), functioning in the X-ray region, extends the capability of the satellite to sense X-rays of high energy in 10-100 keV range.
• v) Scanning Sky Monitor (SSM), is intended to scan the sky for long term monitoring of bright X-ray sources in binary stars, and for the detection and location of sources that become bright in X-rays for a short duration of time.

9. The Fermi Gamma-ray Space Telescope (FGST)

Formerly called the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. The main instrument of FGST is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter.

Data Analysis Teqniques

1. 1. Image Reduction and Analysis Facility (IRAF): Is a software package was developed by National Optical Astronomy Observatory (NOAO) that is used for reduction of astronomical data that is images in pixel array form. IRAF is a well known system with many applications which is in wide use within the astronomical community [6]. It is available for all major operating systems, though it is written for UNIX-like operating systems; we can use it on Microsoft Windows also. It is primarily used on Linux distributions, with a growing share of Mac OS X users. IRAF commands (known as tasks) are organized into package structures. Extra packages may be added to IRAF. Packages may contain other packages. There are many packages available by NOAO and external developers usually focusing on a specific branch of research or facility.
2. 2. Chandra Interactive Analysis of Observations(CIAO): It is system of tools and applications developed by Chandra X-ray Center Science Data Systems (SDS) and Data Systems (DS) teams to assist users in the reduction and analysis of x-ray data from Chandra X-ray Observatory [7]. CIAO is a comprehensive software suite designed with processing Chandra data in mind [8]. We use CIAO tools in the first stages of preparing Chandra imagery for scientific and public use [9]. The CIAO design allows close interconnection of tools. As an example the modeling and fitting tool Sherpa is central of the CIAO system. Sherpa performs fitting and modeling of data in N dimensions, plotting tool ChIPS provides high-quality screen and hardcopy plots from both interactive and scriptable interfaces. In order to allow users of Chandra data to use pre-existing tools, all CIAO tools read and write many formats, as well as FITS images and tables and IRAF imh files.
3. 3. The Science Analysis System (SAS):

The Science Analysis System (SAS) is an assortment of tasks, scripts and libraries, specially designed for the reduction and analysis of data collected by the XMM-Newton observatory.

It is found that XMM-Newton data are offered in two formatso, Observation Data Files (ODF), i.e. FITS format. And Pipeline Processing System (PPS) products

Even if one starts the analysis of an XMM-Newton datasets with the PPS products, the SAS is important to extract standard (spectra, light curves) and customized science products. Moreover, SAS permits the users to reproduce the reduction pipelines run to get the PPS products from the ODFs files.

4. The Astronomical Image Processing System (AIPS):

It is a software package which supports the reduction and analysis of data taken from radio telescopes. It is originally written in FORTRAN 66 but it is has used FORTRAN 77 since 1989. At very first AIPS was installed on a MODCOMP computer, but the package's portability has led to it being installed on many different systems. Pre-compiled versions are now a day is available for users of Linux, Mac OS and Solaris. In 1983, when AIPS was selected as the primary data reduction package for the Very Long Baseline Array (VLBA), the scope of the AIPS effort was expanded to embrace all stages of radio interferometric calibration, both continuum and spectral line. The AIPS package contains a full suite of calibration and editing functions for both VLA and VLBI data, including interactive and batch methods for editing visibility data.

5. Common Astronomy Software Applications (CASA)

This package was developed with the primary aim to support the data post-processing needs of the next generation of radio astronomial telescopes such as VLA and ALMA The package can process both interferometric and single dish data. The CASA consists of a group of C++ tools binded together under an iPython interface as data reduction tasks. This structure provides flexibility to process the data via task interface or as a python script. CASA is developed by an international consortium of scientists based at the National Radio Astronomical Observatory (NRAO), the European Southern Observatory (ESO), the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), the National Astronomical Observatory of Japan (NAOJ), the CSIRO division for Astronomy and Space Science (CASS), and the Netherlands Institute for Radio Astronomy (ASTRON) under the guidance of NRAO.

6. HEASARC Software

This software is used for data analysis in high energies like X-ray and gamma rays, it is supported by following additional software’s. Most of this software’s are designed for professional researchers and advanced students for the analysis of scientific astronomical observations in FITS format.

HEASARC Software Packages:

• SAOImage DS9 - Astronomical Imaging and Data Visualization Application: DS9 supports FITS images and binary tables, multiple frame buffers, region manipulation, and many scale algorithms and color maps.
• Sky View-In-A-Jar - Running Sky View on your own computer.
• XANADU - Suite of spectral (xspec), timing (xronos), and image (ximage) analysis programs.
• XSELECT - Multipurpose tool for filtering event files and generating images, spectra, and light curves. Distributed as part of the HEASARC package on the download page.
• XSTAR - Program for calculating physical conditions and emission spectra in photo ionized gases. FITSIO - A subroutine library for reading and writing FITS files for C and FORTRAN programmers.
• FTOOLS - General FITS file utility programs and mission-specific data analysis tools.
• FV - Interactive editor and viewer for astronomical data files in FITS format. Also provides access to Hera.
• HEAsoft - A unified release of the FTOOLS and XANADU packages.
• Hera - Run the FTOOLS and XANADU software on the Hera servers at the HEASARC, without having to install the software packages locally.
• Maki - Displays fields of view for various instruments on FITS images. Currently supports the Suzaku XIS & HXD, Chandra ACIS & HRC, XMM EPIC, and RXTE PCA detectors.
• PIMMS - Program to estimate count rates from fluxes or vice versa, or to estimate count rates in one instrument from those measured in another.
• Profit - GUI tool for visualizing and modeling high-resolution spectra.

Conclusion

By studying the universe across the electromagnetic spectrum we will get lot of understanding of objects in space. The light from each part of the electromagnetic spectrum brings us important and distinctive information. X-rays and gamma rays bring us information regarding high energy phenomena like black holes, hot gas, supernova remnants and neutron stars. Ultraviolet light reveals hot stars and quasars, where as visible light shows us warmer stars, planets, nebulae, and galaxies. In the infrared we see cool stars, regions of star birth, cool dusty regions of space, and the core of our galaxy. Radiation in the radio region shows us cold molecular clouds and therefore the radiation left over from the big bang, which gives information regarding birth of the universe.

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