How to query posts from specific authors and categories using WP_query?

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$query = new wp_query($arr);
    $arr = array(
        'author__in'=> array(2,4,6), //Authors's id's you like to include
        'posts_per_page' => '12',
        'paged' => $paged,
        'tax_query' => array(
        array(
        'taxonomy' => 'category',
        'field' => 'id',
        'terms' => array ( $cat_ids ),
        )
    )
    );