It will require an object when it is followed by the preposition "a" and meaning to be grateful to someone without giving the reason, like the sentence above. It will not require an object when used to express gratefulness for something that was done. Example: "Ele agradeceu o convite", "He thanked the invitation".
Think of it this way: it means something more like 'give thanks' in English, which, unlike the verb 'thank' in English, is intransitive. I think that you'll find that 'We give thanks to the judge' is a more accurate literal translation.
Keep in mind that not everything maps one-to-one between languages.
It's wrong. You should use "agradecer + a + someone".
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