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Green Peas (GPs) are young, compact, star-forming dwarf galaxies, and local (z~0.3) analogues of the early galaxies (z>6) considered to be mainly responsible for the reionisation of the Universe. Recent X-ray observations of GPs have detected high excess emission which cannot be accounted for by star formation alone, and implies presence of an active galactic nucleus (AGN). We employ radio observations to study the radio properties of GPs, build their radio spectral energy distributions, and verify the presence of AGNs. We performed new radio observations of three GPs with the Karl G. Jansky Very Large Array (JVLA) in the L, C, and X bands (1.4, 6 and 10 GHz resp.), supplemented by the data from archival observations and large radio surveys. We also analysed the archival radio data for a larger sample of GPs and blueberry (BBs) galaxies, which are lower-mass and lower-redshift analogues of the GPs. To understand the significance of the radio observations, we assess the detectability of these sources, and compare the detected radio luminosities with the expectations from theoretical and empirical relations. Two of the three targeted GPs were strongly detected ($>10\sigma$) in the JVLA observations and their fluxes are consistent with star formation, while the third source was undetected. Although a large fraction (~75%) of the sources from the larger archival sample of GPs and BBs could be detected with archival surveys, only a small number (<40%) are detected and their radio luminosity is significantly lower than the expectation from empirical relations. Our results show that the majority of the dwarf galaxy sample is highly underluminous. Especially towards the lower end of galaxy mass and star formation rate (SFR), the radio luminosity-SFR relation deviates from the empirical relations, suggesting that the relations established for larger galaxies may not hold towards the low-mass end., Comment: 9 pages, 4 figures, accepted for publication to A&A

We report LOFAR and VLA detections of extended radio emission in the spiral galaxy HCG 97b, hosted by an X-ray bright galaxy group. The extended radio emission detected at 144 MHz, 1.4 GHz and 4.86 GHz is elongated along the optical disk and has a tail that extends 27 kpc in projection towards the centre of the group at GHz frequencies or 60 kpc at 144 MHz. Chandra X-ray data show two off-nuclear ultra-luminous X-ray sources (ULXs), with the farther one being a plausible candidate for an accreting intermediate-mass black hole (IMBH). The asymmetry observed in both CO emission morphology and kinematics indicates that HCG 97b is undergoing ram-pressure stripping, with the leading side at the southeastern edge of the disk. Moreover, the VLA 4.86 GHz image reveals two bright radio blobs near one ULX, aligning with the disk and tail, respectively. The spectral indices in the disk and tail are comparable and flat ($\alpha > -1$), suggesting the presence of recent outflows potentially linked to ULX feedback. This hypothesis gains support from estimates showing that the bulk velocity of the relativistic electrons needed for transport from the disk to the tail is approximately $\sim 1300$ $\rm km~s^{-1}$. This velocity is much higher than those observed in ram-pressure stripped galaxies ($100-600$ $\rm km~s^{-1}$), implying an alternative mechanism aiding the stripping process. Therefore, we conclude that HCG 97b is subject to ram pressure, with the formation of its stripped radio tail likely influenced by the putative IMBH activities., Comment: 19 pages, 18 figures. Accepted for publication in MNRAS

We use Chandra X-ray data and Very Large Array radio observations for a sample of 20 nearby, massive, X-ray bright, early-type galaxies to investigate the relation between the Bondi accretion rates and the mechanical jet powers. We find a strong correlation ($\rho = 0.96^{+0.03}_{-0.09}$; BF$_{10} > 100$) between the Bondi accretion power, $P_{\text{Bondi}}$, and the mechanical jet power, $P_{\text{jet}}$, for a subsample of 14 galaxies, which also host cool H$\alpha$+[NII] line emitting gas and thus likely have thermally unstable atmospheres. The relation between the Bondi accretion power and the mechanical jet power for this subsample is well described by a power-law model $\log \frac{P_{\mathrm{Bondi}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}} = \alpha + \beta \log \frac{P_{\mathrm{jet}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}}$, where $\alpha = 1.10 \pm 0.25$ and $\beta = 1.10 \pm 0.24$ with an intrinsic scatter $\sigma = 0.08^{+0.14}_{-0.06}$ dex. The results indicate that in all galaxies with thermally unstable atmospheres the cooling atmospheric gas feeds the central black holes at a similar jet-to-Bondi power ratio. For the full sample of 20 galaxies, the correlation is weaker and in a subset of galaxies with no signs of H$\alpha$+[NII] emission, we see a hint for a systematically lower jet-to-Bondi power ratio. We also investigate the dependence of jet power on individual quantities in the Bondi formula such as the supermassive black hole mass ($M_{\bullet}$) and the specific entropy of the gas ($K$) at the Bondi radius. For the subsample of H$\alpha$+[NII] emitting galaxies, we find a very tight correlation of $P_{\text{jet}}$ with $M_{\bullet}$ ($\rho = 0.91^{+0.06}_{-0.11}$; BF$_{10} > 100$) and, although poorly constrained, a hint of an anti-correlation for $P_{\text{jet}}$ and $K$ ($\rho = -0.47^{+0.60}_{-0.37}$; BF$_{10} = 1.1$)., Comment: accepted for publication in MNRAS

Many massive early-type galaxies host central radio sources and hot X-ray atmospheres indicating the presence of radio-mechanical active galactic nucleus (AGN) feedback. The duty cycle and detailed physics of the radio-mode AGN feedback is still a matter of debate. To address these questions, we present 1-2 GHz Karl G. Jansky Very Large Array (VLA) radio observations of a sample of the 42 nearest optically and X-ray brightest early-type galaxies. We detect radio emission in 41/42 galaxies. However, the galaxy without a radio source, NGC 499, has recently been detected at lower frequencies by the Low-Frequency Array (LOFAR). Furthermore, 27/42 galaxies in our sample host extended radio structures and 34/42 sources show environmental interactions in the form of X-ray cavities. We find a significant correlation between the radio flux density and the largest linear size of the radio emission and between the radio power and the luminosity of the central X-ray point-source. The central radio spectral indices of the galaxies span a wide range of values, with the majority of the systems having steep spectra and the rest flat spectra. These results are consistent with AGN activity, where the central radio sources are mostly switched on, thus the duty cycle is very high. 7/14 galaxies with point-like radio emission (Fanaroff-Riley Class 0; FR 0) also show X-ray cavities indicating that, despite the lack of extended radio structures at 1-2 GHz, these AGN do launch jets capable of inflating lobes and cavities.

We present an archival analysis of Chandra X-ray observations for twelve nearby early-type galaxies hosting radio sources with radio power $>10^{23} \, \rm{W}~\rm{Hz}^{-1}$ at 1.4 GHz, similar to the radio power of the radio source in NGC 4261. Previously, in a similar analysis of eight nearby X-ray and optically-bright elliptical galaxies, Werner et al. 2012, found that NGC 4261 exhibited unusually low central gas entropy compared to the full sample. In the central 0.3 kpc of NGC 4261, the ratio of cooling time to freefall time ($t_{\rm{cool}}/t_{\rm ff}$) is less than $10$, indicating that cold clouds may be precipitating out of the hot ambient medium and providing fuel for accretion in the central region. NGC 4261 also hosts the most powerful radio source in the original sample. Because NGC 4261 may represent an important phase during which powerful feedback from a central active galactic nucleus (AGN) is fueled by multiphase condensation in the central kpc, we searched the Chandra archive for analogs to NGC 4261. We present entropy profiles of those galaxies as well as profiles of $t_{\rm{cool}}/t_{\rm ff}$. We find that one of them, IC 4296, exhibits properties similar to NGC 4261, including the presence of only single phase gas outside of $r \sim 2$ kpc and a similar central velocity dispersion. We compare the properties of NGC 4261 and IC 4296 to hydrodynamic simulations of AGN feedback fueled by precipitation. Over the course of those simulations, the single phase galaxy has an entropy gradient that remains similar to the entropy profiles inferred from our observations., Comment: 13 pages, 5 Figures, revised version of paper submitted to ApJ

We present a catalog of compact double radio galaxies (hereafter COMP2$CAT$) listing 43 edge-brightened radio sources whose projected linear size does not exceed 60 kpc, the typical size of their host galaxies. This is the fifth in a series of radio source catalogs recently created, namely: FRI$CAT$, FRII$CAT$, FR0$CAT$ and WAT$CAT$, each focused on a different class of radio galaxies. The main aim of our analysis is to attain a better understanding of sources with intermediate morphologies between FR\,IIs and FR\,0s. COMP2$CAT$ sources were selected from an existing catalog of radio sources based on NVSS, FIRST and SDSS observations for having, mainly, i) edge-brightened morphologies, typical of FR\,IIs, ii) redshifts $z < 0.15$ and iii) projected linear sizes smaller than 60 kpc. With radio luminosities at 1.4 GHz $10^{38} \lesssim L_{1.4} \lesssim 10^{41}$ erg s$^{-1}$, COMP2$CAT$ sources appear as the low radio luminosity tail of FR\,IIs. However, their host galaxies are indistinguishable from those of large-scale radio sources: they are luminous ($-21 \gtrsim M_{r} \gtrsim -24$), red, early-type galaxies with black hole masses in the range of $10^{7.5} \lesssim M_{\rm BH} \lesssim 10^{9.5}\, \rm{M}_\odot$. Moreover, all but one of the COMP2$CAT$ sources are optically classifiable as low excitation radio galaxies, in agreement with being the low radio-power tail of FR\,Is and FR\,IIs. This catalog of compact double sources, which is $\sim 47 \%$ complete at $z<0.15$, can potentially be used to clarify the role of compact double sources in the general evolutionary scheme of radio galaxies.

Echelle spectrographs with their high resolution plays important role in determination of characteristics of stellar lines. Wide field of applications is focused mainly on the measurements of precise radial velocity applied in exoplanetary research. In my diploma thesis I am concentrated on the calibration of the Ond\v{r}ejov Echelle Spectrograph at Astronomical Institute of the Czech Academy of Sciences. My role was to investigate the wide field of opportunities how to process the data with the best possible results. Successful reduction was performed by both Image Reduction and Analysis Facility (IRAF) and for Open source Pipeline for ESPaDOnS Reduction and Analysis. This thesis includes the comparison of both pipelines.