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A Compact Symmetric Object Discovered by the VLA Low-band Ionosphere and Transient Experiment

Kristina Nyland, Mary Rachelle Barrett, Genna Crom, Pallavi Patil, Emil Polisensky, Wendy Peters, Simona Giacintucci, Tracy Clarke, Mark Lacy, Shyaam Mukundan, Dillon Z. Dong, Andy Goulding, Amy E Kimball, Magdalena Kunert-Bajraszewska

TL;DR

The paper addresses identifying compact, young radio AGN and CSOs to understand early jet formation and evolution. It combines commensal 340 MHz VLITE data with VLBA imaging to identify and characterize J0330-2730 as a MHz-peaked spectrum CSO candidate. VLBA reveals a 64 pc double-lobed structure and ~20% 340 MHz variability over ~1 year, with variable Doppler boosting ruled out in favor of refractive interstellar scintillation or variable free-free absorption. The measured lobe size lies below the turnover-size relation for standard SSA jets, suggesting departures possibly due to transient jet formation (e.g., tidal disruption) or a frustrated jet in a dense medium, and illustrating VLITE's utility for discovering compact young sources.

Abstract

We present new Very Long Baseline Array (VLBA) imaging of a MHz-peaked spectrum (MPS) source that was found using commensal low-frequency data taken with the Karl G. Jansky Very Large Array (VLA). The source, J0330-2730, was identified in multi-epoch data from the VLA Low-band Ionosphere and Transient Experiment (VLITE). VLITE continuously collects low-frequency data at 340 MHz during regular VLA observations. Our analysis of the VLITE light curve demonstrates that J0330-2730 has significant 340 MHz flux variability at the ~20% level over a timescale of approximately one year. Our VLBA images reveal a resolved, double-lobed morphology with a projected linear size of 64 pc. We consider plausible mechanisms that could explain the observed 340 MHz variability and the source properties on milliarcsecond scales. We rule-out variable Doppler boosting and conclude that refractive interstellar scintillation or variable free-free absorption are the most likely explanations. We argue that the properties of J0330-2730 are consistent with the class of compact symmetric objects (CSOs) and consider the evolutionary stage of the source. The extent of the resolved lobes revealed by the VLBA is significantly smaller than predictions based on the turnover-size relation for a standard synchrotron self-absorbed jet model. We discuss possible explanations for the departure from the turnover-size relation, including jet formation by a transient phenomenon such as a tidal disruption event or a "frustrated jet" impeded by the presence of dense gas or a high-pressure environment. This study highlights the potential of VLITE for the identification of compact and young radio sources.

A Compact Symmetric Object Discovered by the VLA Low-band Ionosphere and Transient Experiment

TL;DR

The paper addresses identifying compact, young radio AGN and CSOs to understand early jet formation and evolution. It combines commensal 340 MHz VLITE data with VLBA imaging to identify and characterize J0330-2730 as a MHz-peaked spectrum CSO candidate. VLBA reveals a 64 pc double-lobed structure and ~20% 340 MHz variability over ~1 year, with variable Doppler boosting ruled out in favor of refractive interstellar scintillation or variable free-free absorption. The measured lobe size lies below the turnover-size relation for standard SSA jets, suggesting departures possibly due to transient jet formation (e.g., tidal disruption) or a frustrated jet in a dense medium, and illustrating VLITE's utility for discovering compact young sources.

Abstract

We present new Very Long Baseline Array (VLBA) imaging of a MHz-peaked spectrum (MPS) source that was found using commensal low-frequency data taken with the Karl G. Jansky Very Large Array (VLA). The source, J0330-2730, was identified in multi-epoch data from the VLA Low-band Ionosphere and Transient Experiment (VLITE). VLITE continuously collects low-frequency data at 340 MHz during regular VLA observations. Our analysis of the VLITE light curve demonstrates that J0330-2730 has significant 340 MHz flux variability at the ~20% level over a timescale of approximately one year. Our VLBA images reveal a resolved, double-lobed morphology with a projected linear size of 64 pc. We consider plausible mechanisms that could explain the observed 340 MHz variability and the source properties on milliarcsecond scales. We rule-out variable Doppler boosting and conclude that refractive interstellar scintillation or variable free-free absorption are the most likely explanations. We argue that the properties of J0330-2730 are consistent with the class of compact symmetric objects (CSOs) and consider the evolutionary stage of the source. The extent of the resolved lobes revealed by the VLBA is significantly smaller than predictions based on the turnover-size relation for a standard synchrotron self-absorbed jet model. We discuss possible explanations for the departure from the turnover-size relation, including jet formation by a transient phenomenon such as a tidal disruption event or a "frustrated jet" impeded by the presence of dense gas or a high-pressure environment. This study highlights the potential of VLITE for the identification of compact and young radio sources.

Paper Structure

This paper contains 5 sections, 2 figures.

Table of Contents

  1. Introduction
  2. Identifying Young Jets
  3. Compact Symmetric Objects
  4. Data
  5. VLITE

Figures (2)

  • Figure 1: Deep 340 MHz VLITE image centered on the HUDF (Polisensky et al., in prep.). The 1$\sigma$ rms noise level is 158 $\mu$Jy beam$^{-1}$. The image has dimensions of 2$^{\circ} \times 2^{\circ}$ with synthesized beam dimensions of $\theta_{\rm maj} \times \theta_{\rm min} = 8.8^{\prime \prime} \times 3.8^{\prime \prime}$. A zoomed-in view of VLITE_A J033051.4-273014 (J0330-2730) is shown in the 100$^{\prime \prime} \times 100^{\prime \prime}$ inset in the upper right.
  • Figure 2: Optical griz image cutout from DR10 of the Dark Energy Camera Legacy Survey (DECaLS; dey+19). The image has dimensions of 65$^{\prime \prime}$$\times$ 65$^{\prime \prime}$. The green circle has a diameter of 1$^{\prime \prime}$ and is centered on the VLBA position of J0330-2730.