How do I write a Django query with a subquery as part fo the WHERE clause?

I'm using Django and Python 3.7. I'm having trouble figuring out how to write a Django query where there's a subquery as part of a where clause. Here's the models ...

class Article(models.Model):
    objects = ArticleManager()
    title = models.TextField(default='', null=False)


class ArticleStat(models.Model):
    objects = ArticleStatManager()
    article = models.ForeignKey(Article, on_delete=models.CASCADE, related_name='articlestats')
    elapsed_time_in_seconds = models.IntegerField(default=0, null=False)
    votes = models.FloatField(default=0, null=False)


class StatByHour(models.Model):
    index = models.FloatField(default=0)
    # this tracks the hour when the article came out
    hour_of_day = IntegerField(
        null=False,
        validators=[
            MaxValueValidator(23),
            MinValueValidator(0)
        ]
    )

In PostGres, the query would look similar to

select * FROM article a, articlestat ast where a.id = ast.article_id and ast.votes > 100 * (select index from statbyhour where hour_of_day = extract(hour from a.created_on))

Notice the subquery as part of the WHERE clause

ast.votes > 100 * (select index from statbyhour where hour_of_day = extract(hour from a.created_on))    

So I thought I could do something like this ...

hour_filter = Func(
    Func(
        (F("article__created_on") + avg_fp_time_in_seconds * "interval '1 second'"),
        function='HOUR FROM'),
    function='EXTRACT')
...
votes_criterion2 = Q(votes__gte=F("article__website__stats__total_score") / F(
    "article__website__stats__num_articles") * settings.TRENDING_PCT_FLOOR *
                                StatByHour.objects.get(hour_of_day=hour_filter) * day_of_week_index)
qset = ArticleStat.objects.filter(votes_criterion1 & votes_criterion2,
                                  comments__lte=25)

but this results in a "Cannot resolve keyword 'article' into field. Choices are: hour_of_day, id, index, num_articles, total_score" error. I think this is because Django is evaulating my "StatByHour.objects" query before the larger query within it is run, but I don't know how to rewrite things to get the subquery to run at the same time.

Edit: K, moved my subquery into an actual "Subquery" function and referenced the filter I created using OuterRef ...

hour_filter = Func(
    Func(
        (F("article__created_on") + avg_fp_time_in_seconds * "interval '1 second'"),
        function='HOUR FROM'),
    function='EXTRACT')
query = StatByHour.objects.get(hour_of_day=OuterRef(hour_filter))


...
votes_criterion2 = Q(votes__gte=F("article__website__stats__total_score") / F(
    "article__website__stats__num_articles") * settings.TRENDING_PCT_FLOOR *
                                Subquery(query) * 
                 day_of_week_index)
qset = ArticleStat.objects.filter(votes_criterion1 & votes_criterion2,
                                  comments__lte=25)

and this results in an

This queryset contains a reference to an outer query and may only be used in a subquery.

which is odd because I am using it in a subquery.

Edit #2: Even after changing the query per the answer given ...

hour_filter = Func(
    Func(
        (F("article__created_on") + avg_fp_time_in_seconds * "interval '1 second'"),
        function='HOUR FROM'),
    function='EXTRACT')
query = StatByHour.objects.filter(hour_of_day=OuterRef(hour_filter))[:1]

...
votes_criterion2 = Q(votes__gte=F("article__website__stats__total_score") / F(
    "article__website__stats__num_articles") * settings.TRENDING_PCT_FLOOR *
                                Subquery(query) *
                                day_of_week_index)
qset = ArticleStat.objects.filter(et_criterion1 & et_criterion2 & et_criterion3,
                                  votes_criterion1 & votes_criterion2,
                                  article__front_page_first_appeared_date__isnull=True,
                                  comments__lte=25)

I still get the error

'Func' object has no attribute 'split'

from How do I write a Django query with a subquery as part fo the WHERE clause?