Chapter1.tex

\chapter{Introduction}
\label{Chap1}
\lhead{\emph{Chapter 1: Introduction}} % Write in your own chapter title to set the page header
\noindent

%As a sentient species with an indomitable spirit of curiosity, we human beings have pondered over innumerable things throughout our existence.
%Many of our ruminations have been directed at the universe we live in, perhaps drawn by the beauty of a night sky with perplexing blue dots and its mysterious, beckoning vastness.
%This process has led to numerous concepts of the universe that were hatched and evolved in many minds through millennia.
%In the early days, while we had numerous imaginative conceptions about the cosmos, the ideas with testable predictions were few.
%However, robust ideas evolved as time progressed and gave rise to new ideas and explorations due to their testable nature---the small pool of testable ideas grew and became known as science.

%The evolution of testable ideas into science can be best explained with astronomy.
%Historically, astronomy was indistinguishable from astrology.
%Celestial objects were studied for their supposed influence on earthly events and human life\footnote{Our tendency to conflate life with the motion of celestial bodies may stem from humanity's innate quest for meaning, aptly captured by Immanuel Kant: "The human heart refuses to believe in a universe without a purpose".}.
%Today, astronomy is a major scientific discipline that significantly enhances our understanding of the universe.
%We learned that our place in the universe is not unique by observing the heavens (this concept is known as the Copernicus principle, but see \citealt{caldwell2008test}).
%Modern astronomical telescopes on Earth and in space utilise cutting-edge technologies, such as the James Webb Space Telescope (JWST; \citealt{sabelhaus2004overview}).
%From our seemingly average vantage point, we have gazed and pondered over the stars, then looked over to the distant galaxies, galaxy clusters, and large voids.
%Our gaze has even reached the cosmic microwave background radiation, the light emitted very shortly after the Big Bang \citep{collaboration2020planck}.
%Powerful telescopes and computational resources have enabled us to accumulate colossal amounts of astronomical observational data.
%
%Astronomical observations have opened up a Pandora's box---while we have come far in understanding the cosmic wonders made bare by the extensive data, many mysteries remain.
%Current observations have revealed that our universe contains pockets of light called galaxies, which host nearly all stars.
%We reside in one such galaxy, known as the Milky Way.
\revii{Astronomers have studied galaxies since their discovery to unravel the complex physical processes behind their formation and evolution.}
The galaxies we observe today are thought to be the present manifestations of density perturbations in the early universe, as described by the currently favoured $\Lambda$CDM model (\citealt{mccaffrey2023no}, but also see \citealp{del2017small} and \citealt{adamo2024first}).
Despite significant advances, many challenges remain in deciphering galaxy formation and evolution, with one of the most complex being the process of star formation---how does the low-density gas collapse to form stars with densities that are many orders of magnitudes higher?
The observational data can be used to find clues that may answer part of the multifaceted problem of star formation.
%Observations show us that, although star formation is mostly observed to be present in galaxies, a small fraction can be found in tails and clouds of gas left behind by galaxy-galaxy interactions.
%Famous examples are the Atoms-for-peace galaxy and Stephan's Quintet \citep{george2018dissecting, xu2005ultraviolet}.
In some galaxies (e.g., \citealt{shin2019positive, cresci2015ngc5643, joseph2022uvit}), star formation is found to be associated with active galactic nuclei or AGN (a phase of supermassive black holes hosted in the central regions of galaxies that produce immense amounts of energy by mass accretion).
The relationship between AGN activity and star formation is particularly fascinating, as observations indicate that AGN can both trigger and suppress star formation in galaxies.
%Studying star formation in such varied and extreme environments may provide valuable insights to unravel the physics behind it and help to understand star formation in these environments.

There is a scarcity of spatially resolved studies investigating the influence of AGN on star formation activity in nearby galaxies.
Therefore, we utilised high spatial resolution imaging data to explore how AGN activity shapes star formation in galaxies.
Specifically, we studied a sample of three nearby galaxies---Cen A, NGC 3982, and NGC 628 (all within < 16 Mpc)---to evaluate the role of AGN in regulating star formation.
For this purpose, we used ultraviolet observations from Ultraviolet Imaging Telescope (UVIT) and Galaxy Evolution Explorer (GALEX), supplemented with multiwavelength information, to derive a meaningful picture of the star formation activity in these galaxies.
The excellent imaging capability of UVIT on board the \textit{AstroSat} space observatory is evident in the high-resolution images and the derived science presented in this contribution.

The remainder of this chapter provides an overview of star formation and the impact of AGN on this process.
It also explains the significance of ultraviolet observations for studying star formation. Additionally, we highlight the importance of multiwavelength data in enhancing our study.
The chapter concludes with a comprehensive literature review and outlines the various motivations for this thesis work.

\section{Overview of star formation}

\begin{figure}
	\centering
	\includegraphics[width=1\columnwidth]{Introduction/ngc_3603_marked.pdf}
	\caption{Hubble Space Telescope Wide Field and Planetary Camera 2 (HST WFPC2) image of NGC 3603 is shown with F656N filter in yellow and F658N in blue colours.
		A molecular cloud (1), a proplyd (2, \citealt{brandner2000hst}), cluster of stars (3), blue supergiant Sher 25 (4, \citealt{brandner1997ring}), and interstellar medium (ISM, 5) are marked in the figure to represent various stages of the matter cycle in the Universe.
		Young stars form from molecular clouds, evolve through the main sequence, finally end their life as supernovae or planetary nebulae by losing mass to the surrounding ISM.
		North is up, and east is towards the left.}
	\label{fig:matterCycle}
\end{figure}

Star formation takes place due to the gravitational collapse of molecular clouds.
The molecular clouds themselves are formed by cooling the neutral hydrogen gas.
Fig.~\ref{fig:matterCycle} shows the matter cycle in the Universe, where the matter in the gaseous phase gets converted to stars and planets and then back into the gaseous phase.
The figure highlights various components---a molecular cloud, a proplyd \citep{brandner2000hst}, a cluster of stars, the blue supergiant Sher 25 \citep{brandner1997ring}, and the interstellar medium (ISM)---representing different stages of the matter cycle.
The arrows circularly connecting the highlighted components of the figure denote the matter cycle.
Young stars form from the molecular clouds, evolve through the main sequence, and finally end their life as supernovae or planetary nebulae by losing mass to the surrounding ISM.
This cycle involving star formation repeats in the Universe.

The Jeans mass ($M_J$), named after James Jeans for his work studying the stability of nebulae \citep{jeans1902stability}, is a useful mathematical concept to understand how gravity can overcome the gas pressure in gas clouds leading to its collapse.
The Jeans mass $M_J$ is given by the following formula:
\begin{equation}
M_J = \left( \frac{5 k_B T}{G \mu m_p} \right)^{3/2} \left( \frac{3}{4 \pi \rho} \right)^{1/2}
\end{equation}
where $k_B$ is the Boltzmann constant, $T$ is the temperature of the gas cloud, $G$ is the gravitational constant, $\mu$ is the mean molecular weight of the gas (in units of proton mass), $m_p$ is the proton mass, and $\rho$ is the density of the gas cloud.
The Jeans mass represents the mass at which gravitational forces overcome the internal pressure, causing the cloud to collapse. If the cloud's mass exceeds the Jeans mass, it becomes gravitationally unstable and collapses.
On the other hand, if the mass is below this threshold, thermal pressure will prevent collapse, and the cloud remains stable.

For molecular clouds with temperatures of $10-30$ K and number densities around $10^2-10^4$ $\text{n(H$_2$)$/$cm}^3$ \citep{mac2004control}, the Jeans mass lies between $\sim$$10-400$ M$_\odot$.
Observations indicate that the mass of these clouds typically falls within the range of $10^2-10^4$ M$_\odot$, suggesting that most molecular clouds should be actively forming stars.
However, this would imply unrealistically high rates of star formation, which contradicts observations \citep{zuckerman1974radio}.
Resolving this discrepancy remains an active area of research.
It is believed that a combination of factors helps keep star formation efficiencies low in galaxies.
A widely accepted explanation is that turbulence plays a critical role in reducing star formation efficiency, while magnetic fields and feedback processes provide additional suppression \citep{mckee2007theory}.


The numerous factors affecting star formation make it a complex and chaotic process to study.
However, significant progress has been made through observations, theoretical studies, and simulations.
Stars typically form in groups or clusters and are often found to have companions  \citep{duchene2013stellar}.
\revii{The initial distribution of stellar masses in such groups or clusters typically follows a pattern known as the Initial Mass Function (IMF)}, with fewer massive stars compared to their lower-mass counterparts  \citep{ salpeter1955luminosity, kroupa2001variation}.
The rate at which the gas is converted to stars is a time-dependent parameter that varies drastically between regions of a galaxy and across galaxies \citep{kennicutt2012star}.

%Many factors can affect star formation in galaxies.
%Some such  are galaxy-galaxy interactions and mergers \citep{lambas2012galaxy}, ram pressure stripping in galaxy clusters \citep{george2018GASP}, stellar winds \citep{gatto2017silcc}, and AGN \citep{fabian2012observational}.

\section{Active galactic nuclei}
Supermassive black holes (SMBHs, $10^6$--$10^{10}$ M$_\odot$) are present in the central region of almost all galaxies, and their properties are closely  associated with the host galaxy properties \citep{magorrian1998demography, gebhardt2000relationship, ferrarese2000fundamental, gultekin2009m, kormendy2013coevolution}.
Therefore, the evolution of SMBHs and host galaxies are thought to be related.
SMBHs can generate copious amounts of energy through accretion \citep{abramowicz2013foundations}.
This energetic phase of SMBHs is known as AGN.
AGN energy production tends to be highly variable, with individual phases of AGN activity typically lasting around $10^5$ years \citep{schawinski2015active}.

A theoretical luminosity limit of spherically symmetric accretion can be calculated by equating outward radiation pressure with inward gravitational force.
This limit is called Eddington luminosity (L$_{Edd}$) = $1.25\times10^{38}\ \text{M}_{BH}$, where M$_{BH}$ is the black hole mass in the solar mass unit (M$_{\odot}$, \citealt{rybicki1991radiative}).
The observed bolometric luminosity (L$_{bol}$) is compared against L$_{Edd}$ to characterise the accretion efficiency in AGN.
The L$_{bol}$$/$L$_{Edd}$ ratio is known as the Eddington ratio.

AGN energy release modes are classified into radiative (also known as quasar, wind, or radiatively efficient) and mechanical (also known as radio, jet, or radiatively inefficient) modes \citep{harrison2017impact, harrison2024observational}.
This dichotomy primarily stems from the accretion efficiency indicated by the Eddington ratio.
The radiative mode is associated with high Eddington ratios ($>$1\%), while the mechanical mode corresponds to low ratios ($<<$1\%).
In the radiative mode, the energy release is dominated by energetic photons, leading to ionization of the gas and radiation-driven ionized gas outflows.
Conversely, in the mechanical mode, energy release is dominated by energetic particles.

\section{The effect of active galactic nuclei on star formation}

The energy released by AGN (E$_\text{bh}$) can be $\sim$100 times more than the binding energy of the host galaxy (E$_\text{gal}$, \citealt{fabian2012observational}).
Therefore, even if a fraction of the AGN energy output is imparted on the galaxy's gas content, it can profoundly affect star formation.
AGN may play a crucial role in galaxy evolution by quenching star formation in galaxies \citep{springel2005black, di2005energy, somerville2008semi, beckmann2017cosmic}.
While the enormous energy output by AGN is thought to suppress star formation by heating the gas (negative AGN feedback), there have been studies that suggest AGN activity can also enhance star formation (positive AGN feedback) in galaxies \citep{zinn2013active}.




Observations have demonstrated that both radiative and mechanical modes can suppress or trigger star formation by heating or compressing the gas \citep{shin2019positive, joseph2022active, joseph2022uvit, cresci2015ngc5643, ngc7252george2018uvit}.
High angular resolution observations of star formation in nearby AGN host galaxies can provide detailed insights into these effects, revealing the intricate interplay between AGN activity and galactic evolution.

%AGN can influence star formation in their host galaxies through their substantial energy output, which can heat the surrounding gas reservoir.
%Both radiative and mechanical modes of AGN energy release, such as radiation pressure and jets/outflows, can significantly impact the galaxy star formation.

\section{Study of star formation using ultraviolet observations}
%Observations of star formation can provide insights into understanding the conditions under which stars are formed.
Observational indicators exist to identify and measure ongoing star formation in galaxies \citep{kennicutt2012star, calzetti2013star}.
Commonly used tracers of star formation include ultraviolet (UV) continuum (1250--2800 $\angstrom$) tracing photospheric emission chiefly from O and B-type stars, H$\alpha$ emission line probing photoionised HII regions, and infrared continuum measuring dust-reprocessed stellar radiation.
If there is little or no dust to reprocess the radiation from young stellar populations, the star formation rate (SFR) derived from infrared observations can be an underestimate.
Complicating matters further, dust heated by evolved stellar populations can contribute to infrared emission, leading to an overestimate of the SFR.
Both UV and H$\alpha$ tracers are limited by their susceptibility to dust attenuation. Additionally, H$\alpha$-derived SFRs in regions with low star formation may suffer from significant uncertainties due to the scarcity of O-type stars.

%For example, star formation in an undisturbed galaxy could differ from a galaxy undergoing a merger.
%The Ultraviolet (UV) emission from young stars is among the preferred tracers for studying recent star formation in galaxies \citep{kennicutt2012star}.
%Young stellar populations produce more significant amounts of UV emission than old ones because of the short-lived and UV-bright early-type stars in them.
Young stellar populations being UV bright makes the UV continuum a direct tracer of star formation compared to indirect tracers such as the H$\alpha$ emission line and infrared continuum.
%\cite{kennicutt1998star} demonstrated a quantitative relationship between UV luminosity and SFR in galaxies.
UV emission primarily originates from the photospheres of short-lived ($<$100 Myr), massive  ($\sim$3--100 $M_\odot$) O and B-type stars. Therefore, the UV flux provides a direct measure of recent star formation activity, specifically tracing stars formed within the last $\sim 100$ Myr. \cite{kennicutt1998star} demonstrated a quantitative relationship, under certain assumptions, between the observed UV luminosity ($L_{\text{UV}}$) and the SFR:

\begin{equation}
\text{SFR} (M_\odot \, \text{yr}^{-1}) = 1.4 \times 10^{-28} \, L_{\text{UV}} (\text{ergs s}^{-1} \text{Hz}^{-1})
\end{equation}
%This relation assumes a continuous star formation history and a Salpeter initial mass function (IMF).

The UV radiation is significantly attenuated by Earth's atmosphere---the radiation in the 800--2000 $\angstrom$ range is absorbed by molecular oxygen (O$_2$), while the radiation between 2000--3000 $\angstrom$ is absorbed by ozone (O$_3$) through photodissociation processes in the upper atmosphere \citep{watanabe1958ultraviolet}.
As a result, UV telescopes have to be at very high altitudes to minimize atmospheric attenuation, with many operating in space to avoid these effects altogether.
Among the UV telescopes active in the past and present, data from the GALEX mission has been widely used for star formation studies.
GALEX was a UV survey mission that observed the sky simultaneously in far-ultraviolet (FUV; 4.2 arcseconds full width at half maximum [FWHM]) and near-ultraviolet (NUV; 5.3 arcseconds FWHM) channels \citep{morrissey2007calibration}.
UVIT on board the \textit{AstroSat} observatory \citep{tandon2017firstresults} is another UV telescope that has the capability to observe simultaneously in FUV and NUV channels with a higher spatial resolution than GALEX.

\subsection{Relevance of Ultraviolet Imaging Telescope (UVIT)}
\textit{AstroSat}, launched in 2015, is India’s first dedicated space observatory \citep{singh2014astrosat}.
UVIT is one of the five scientific payloads aboard the observatory.
It can observe simultaneously in the FUV (1300--1800 $\angstrom$), NUV (2000--3000 $\angstrom$) and visible (VIS, 3200--5200 $\angstrom$) channels \reviii{\citep{tandon2017orbit}}.
The VIS channel observations are only used for estimating the telescope pointing drift.
The UV channels operates in the photon counting mode, where photon positions are detected from each detector readout frame using a centroiding algorithm \citep{hutchings2007photon}.
The UV photon counting data are drift corrected using the VIS-channel to derive the final imaging UVIT data products.
Both FUV and NUV \reviii{channels} have a field of view of $\sim$28 arcminutes and an angular resolution of $<$1.5 arcseconds FWHM \reviii{\citep{tandon2020additional}}.
UVIT has a superior spatial resolution compared to GALEX and features selectable filters in FUV and NUV \reviii{channels}.
Despite the loss of the NUV channel in 2018, UVIT continues to observe the sky and will celebrate its ten-year anniversary in 2025.
\newline
\newline
We have used UV observations to get the spatial map of star formation in galaxies.
Using the star formation spatial maps, we studied AGN effects on star formation in galaxies.
We have made use of multi-wavelength data in our study.

\section{Multiwavelength perspective}
To better understand the AGN effects on star formation, we cannot restrict ourselves to UV observations alone.
The AGN activity produces X-ray and radio emissions.
The AGN energy output can affect the gas in or outside the galaxy, leading to the gas emitting in X-ray, radio, optical, and UV wavelengths.
Due to the susceptibility of UV observations to dust attenuation, we require dust attenuation corrections or independent confirmation of the spatial maps of star formation from other wavelengths.
Additionally, there is a need to identify and remove foreground Galactic sources.

We have used multiwavelength data in our study for the above reasons.
A breakdown of the instruments used is provided below as a list, with the instruments classified based on the waveband.

\begin{itemize}
	\item UV
	      \begin{itemize}
		      \item GALEX
		      \item UVIT
	      \end{itemize}
	\item Infrared
	      \begin{itemize}
		      \item James Webb Space Telescope (JWST)
	      \end{itemize}
	\item Optical
	      \begin{itemize}
		      \item Hubble Space Telescope (HST)\footnote{While HST has been classified under the optical category, HST has additional observing capabilities in UV and infrared.}
		      \item Gaia
		      \item Mapping Nearby Galaxies at Apache point observatory (MaNGA)
		      \item Multi Unit Spectroscopic Explorer (MUSE)
	      \end{itemize}
	\item Radio
	      \begin{itemize}
		      \item Atacama Large Millimeter/submillimeter Array (ALMA)
		      \item Murchison Widefield Array (MWA)
		      \item Karl G. Jansky Very Large Array (VLA)
		      \item Parkes radio telescope
	      \end{itemize}
	\item X-ray
	      \begin{itemize}
		      \item Chandra X-ray Observatory
	      \end{itemize}
\end{itemize}

\section{Review of literature}
In the local Universe, SMBHs with a mass range of $\sim$$10^6$--$10^{10}$ M$_\odot$ exist in central region of galaxies \citep{kormendy2013coevolution}.
While the SMBHs occupy negligibly small regions compared to the host galaxy sizes, the active phases of SMBHs (AGN) have significant effects on their hosts called AGN feedback \citep{fabian2012observational, harrison2017impact}.
The star formation in massive galaxies can be regulated by AGN feedback, and it is included in simulations and theoretical models to obtain the observed galaxy properties \citep{binney1995evolving,ferrarese2000fundamental, kauffmann2000unified, springel2005black, di2005energy, somerville2008semi, beckmann2017cosmic}.
In contrast with the star formation suppression through heating of the galaxy gas content (negative AGN feedback), the AGN activity is sometimes associated with positive feedback where AGN feedback triggers star formation \citep{zinn2013active}.

Although evidence for AGN feedback is available, direct observations of its influence on star formation in the local Universe remain limited \citep{kormendy2013coevolution}.
One reason for the scarcity of direct observations could be that AGN luminosities vary considerably during a typical star-forming episode, and the effect of feedback on star formation may not be readily apparent \citep{hickox2014black, harrison2017impact}.
Such variability can give rise to situations where even if a galaxy's star formation were affected by AGN activity, the corresponding signatures of a strong AGN could have become undetectable.
Similarities in star formation efficiencies between Seyfert and inactive local galaxies have been found by \cite{rosario2018llama}.
While this observation may suggest that the AGN activity does not affect star formation efficiencies in AGN host galaxies, it is also possible that the AGN could have been active in the past in inactive galaxies \revii{\citep{harrison2017impact}}.
In studies where the sample of galaxies is selected by AGN activity, obtaining a correlation between the highly variable activity of AGN feedback and star formation that takes place on a relatively long timescale may be challenging.

Recently, \cite{arevalo2024newborn} observed a newborn AGN in a galaxy previously observed not to have any AGN signatures.
The inverse is also possible---galaxies may have had an AGN phase in the recent past but have now been turned off.
If we can find such galaxies and study recent star formation in the central regions and its connection to any recent AGN activity, it may lead to a better understanding of the complex relationship of AGN feedback with star formation.
Such studies might make it possible to find relatively smooth time-variable parameters connected to AGN feedback and explore their relationship with star formation as a proxy to unravel how AGN feedback transforms the galaxy.

Among the observations of AGN feedback affecting star formation in nearby galaxies, there are cases of both positive and negative feedback.
The AGN jet-induced positive feedback is found in galaxies such as Centaurus A, NGC 1275, and Minkowski's Object \citep{mould2000jetCenA, ngc1275canning2010star, van1985minkowski}.
Outflow-induced star formation exists near the nuclear region of NGC 5643 \citep{cresci2015ngc5643}.
In NGC 7252 and the jellyfish galaxy JO201, AGN activity is proposed to have suppressed star formation in the central region \citep{ngc7252george2018uvit, george2019gasp}.
Both positive and negative feedback have been observed in NGC 5728 \citep{shin2019positive}.

High spatial resolution studies of observational signatures of AGN feedback on star formation in nearby galaxies could help unravel the complex spatial and temporal relationship of AGN interaction with its host galaxy environment.
Since AGN are known to impart energy through radiative (sometimes called quasar or wind) and mechanical modes (also known as radio, kinetic, or jet; \citealt{morganti2017many, harrison2017impact}), they leave behind observational signatures that could be identified.
The enormous energy throughput will ionise the gas around AGN and produce excitation lines that can be spatially mapped (see \citealt{penny2018sdss} as an example study).
Similarly, star formation can be suppressed or triggered in the galaxy, which can be observed via the absence or presence of emitted UV flux associated with star formation activity \citep{kennicutt2012star}.
The UV observations have been used to study the AGN impact on star formation \citep{neff2015complex, ngc7252george2018uvit, george2019gasp, rubinur2024study}.

Star-forming rings with centrally suppressed star formation are commonly observed in barred galaxies \citep{erwin2024frequency}.
However, there exist galaxies such as NGC 628 that are not found to have a bar but have ring-like star formation \citep{querejeta2021stellar, hoyer2023phangs}.
AGN feedback can suppress star formation in the central regions of galaxies \citep{gaibler2012jet}.
This has been observed by \cite{ngc7252george2018uvit,joseph2022active, pak2023origin}.
Therefore, AGN activity can be an alternate explanation for ring-like star formation in some galaxies.

\section{Motivation for the study}

Below, we outline our primary motivations for conducting this study.

\subsection{Understand the effect of AGN activity on star formation in nearby galaxies}

The galaxies investigated in this work are nearby, specifically Centaurus A (3.8 Mpc), NGC 3982 (15.6 Mpc), and NGC 628 (9.84 Mpc).
While numerous studies have examined AGN feedback in galaxies, relatively few have focused on nearby galaxies.
The proximity of these galaxies allows for highly spatially resolved studies, enabling a detailed exploration of AGN's impact on star formation.

\subsection{How AGN affects star formation in various galaxy evolutionary stages}
Centaurus A (Cen A) is an active galaxy that underwent a merger $\sim$ 2 Gyr ago, NGC 3982 is a Seyfert spiral galaxy with known AGN activity, and NGC 628 is a spiral galaxy with presently no AGN activity detected.
The galaxies selected for the study are at different stages of evolution.
We are interested in understanding how AGN activity affects star formation in various galaxy evolutionary stages.

\subsection{Investigate the radiative and mechanical modes of AGN feedback effects on star formation}
AGN feedback can manifest in both mechanical and radiative modes, each potentially affecting star formation differently.
In this study, Cen A's AGN operates in the mechanical mode, while NGC 3982's AGN operates in the radiative mode.
By closely examining how these modes affect star formation, we aim to elucidate the distinct impacts they have on their host galaxies.

\subsection{Explore an alternate explanation for ring-like star formation}
Traditionally, ring-like star-forming regions within galaxies are attributed to the effects of bars.
However, recent studies suggest that AGN feedback can also cause ring-like star formation. Notably, both NGC 3982 and NGC 628 exhibit ring-like star formation without the presence of bars.
This study seeks to explore AGN feedback as a potential explanation for these phenomena.
\\

\revii{The remaining chapters present our studies on the effects of AGN activity on star formation in nearby galaxies through observations.
Focusing on nearby galaxies allowed us to spatially resolve these effects.
Since AGN activity manifests in both mechanical and radiative modes, understanding the impact of each mode on star formation is crucial.
Chapter 2 examines the mechanical mode of AGN feedback on star formation in the Cen A galaxy using UVIT observations and multiwavelength data.
Chapter 3 explores the radiative mode of AGN feedback on star formation in the NGC 3982 Seyfert spiral galaxy using GALEX and MaNGA data.
Chapter 4 investigates star formation suppression in NGC 628 to identify signs of recent AGN activity using JWST, MUSE, and UVIT data.
Chapter 5 comprehensively summarises the major findings from these studies.}