I am looking for some direct references in moola vedas that talk of swarga or heaven
Shlomo Bîderman in his book Scripture and Knowledge: An Essay on Religious Epistemology tells us what was the exact idea of swarga during vedic times.
The conception of swarga plays an important if varying function in the vedic literature. Although mentioned only once in Rig-Veda , its profusely mentioned in Atharva Veda , and in the Brahmanas. In the Rig-Veda it is described as a heavenly place of happiness and bliss. However , this description is far cry from superficially similar accounts of "heaven " in other religious traditions. As Gonda remarks , "The vedic swarga is not some kind of Garden of eden before the fall , or the place where to return to innocence , or the abode of the dead. Not surprisingly even in the early vedic period , the notion of swarga was implicated in the idea of srauta ritual as a repetition of the relations governing the cosmos and enabling the human sacrificer to manipulate the world or rather create the universe more as he pleased.
The above is mentioning can be precisely found in Atharva Veda , where a householder and his wife is doing sacrifice for prosperity and happiness on earth and in heaven. Below are the mantras from Atharva veda.
We find direct mentioning of concept of Swarga in of Atharva Veda kanda 12 -Sukta 3- Which is called "SwargaonDana Sukta " - An accompaniment to the preparation and presentation of sacrificial offerings by a householder and his wife, with prayer for prosperity and happiness on earth and in heaven.
Its said in the sukta that Swarga can be attained with yajna and only those are having faith ,attain Swarga Loka. Those gods who are in the subtle from are the carriers i.e. they carry oneself to swarga. (16). The streams which gives the immortality are centered in swarga.
यं वां पिता पचति यं च माता रिप्रन्निर्मुर्क्तै शमलाच्च वाच : |
स ओदन: शतधार: स्वर्ग उभे व्याप् नभसी महित्वा || AV 12.3.5||
That which your mother and your sire, to banish sin and un-cleanness from their lips, are cooking. That Odana with hundred streams, sky-reaching, hath in its might prevaded earth and heaven.
स्वर्गं लोकमभि नो नयासि सं जायया सह पुत्रै: स्याम |
गृह्णामि हस्तमनु मैत्वत्र मा नस्तारीन्न ऋतिर्मो अराति: || AV 12.3.17||
Unto the world of Svarga shalt thou lead us: there may we dwell beside our wife and children. I take thy hand Let not Destruction, let not Malignity come hither and subdue us.
आ यन्ति दिव: पृथिवीं सचन्ते भूम्या : सचन्ते अध्यन्तरिक्षं |
शुद्भा: सतीस्ता उ शुम्भन्त एव ता न: स्वर्गमभि लोकं नयन्तु ||AV 12.3.26||
From heaven they come, they visit earth, and rising from earth unite themselves with air's mid-region, Purified, excellent, they with shine in beauty. Thus may they lead us to the world of Svarga.
Here is English translation of above Mantras.
We also find mentioning of Swarga in Rig Veda Mandala 10 - Sukta 95 - Mantra 18 , Which is actually a dialogue hymns and the mantra 18 is dialogue between Pururava and Urvashi .
इति तवा देवा इम आहुरैळ यथेमेतद भवसिम्र्त्युबन्धुः |
परजा ते देवान हविषा यजाति स्वर्ग उ तवमपि मादयासे || RV 10.95.18||
iti tvā devā ima āhuraiḷa yathemetad bhavasimṛtyubandhuḥ |
prajā te devān haviṣā yajāti svargha u tvamapi mādayāse ||
18 Thus speak these Gods to thee, O son of Iḷā: As death hath verily got thee for his subject, Thy sons shall serve the Gods with their oblation, and thou, moreover, shalt rejoice in Svarga.
And we find mentioning of swarga in Yajurveda Chapter 18 Mantra 54 ,59,60.
दिवे मुर्धासि पृथिव्या नाभिरुर्गपामोषाधिनाम | विश्वायु : शर्म सप्रथा नमस्पथे || YV18.54||
O learned person thou art the heaven's head . The center of he earth , the essence of waters and plants .Thou art the enjoyer of full life of hundred years and full of glory .For right guidance be thou full of food and shelter.
एतं सधस्थ परि ते ददामि यमावहाच्छेवधिं जातवेदा : |
अन्वागन्ता यज्ञपतिर्वो अत्र त स्म जानीत परमे व्योमन ||YV.59||
Ye seekers after god ,and common run of mankind , I the knower of the meaning of vedas ,and guardian of sacrifice ,having realised god ,the treasure of the happiness ,preach unto ye ,the true nature of the god prevading this highest heaven . Know him about whom . I the follower of the religion ,instruct thee.
एतं जानीथ परमे व्योमन् देवा: सधस्था विद रूपमस्य |
यदागच्छ त्पथिभिर्देवयानैरिष्टापुर्ते कृणवाथाविरस्मै ||YV 18.60||
O learned persons ,living together know this god spread in the highest heaven and realise his true nature .he who reaches him through yogic paths of sages ,should reveal to him pious acts pertaining to vedic injunctions and public utility .
Here are the above Yajurveda Mantras English translation by Devi Chand. Here the word Vyoma is Swarga or heaven.
Here is one more mention of Swarga (not mentioned in the other answer) from the Atharva Veda. It is a description of the nine-doored human body as the city of Gods.
TasyA hiranyayah koshah
Swargo jyotishAvrita ||
Nine doored with eight lotuses, is the impregnable stronghold of Gods; In that is a golden vessel which is covered with light and leads to the Heaven.
Atharva Veda 10.2.31
One more from the same Veda:
Yat upari shayanam Aharanti swarga meva tena lokam avarundhe ||
He who prepares a good bed for the guest, indeed reaches Heaven.
Atharva Veda 9.63
Plus there are many references to Swarga in the Krishna Yajurveda (KYV) too. In it, instead of Swarga, Suvarga is used.
SamAnya richo bhavanti manushyaloko va richo manushyolokAdeva na yantyanyadanyatsAma bhavati devaloko vai sAma devolokAdevAnyamanyam manushyalokam pratyavarohanto .....||
KYV KAnda 7, PrapAthaka 5, AnuvAka 4.
Here, Devaloka is used and not Suvarga though.
The meaning of the above Mantra is this - Earth is considered as the plane for actions or the Karma Bhoomi. By virtue of these Karmas the man attains the Heavens. So, the earth forms the basis for the heaven. Likewise the Riks form the bases for the SAmans. So, here the Riks are equated with the earth and the SAmans with the heavens..
NivitAm manushyAm prAchinAvitam pitrinAmupavitam devAnAmupa vyayate devalakshanameva tat kurute tithannanvAh tishthan hyAsrutataram vadati tishthannanvAh suvargasya lokasyAbhijithyA Asino yajatyasminneva loke prati yath...||
KYV KAnda, PrapAthaka 5.
SAyana says here- " "Upavitam vidhAtum prastauti.." ( oR Here it's describing how the performer of Yajna should wear the Upavita)".
The meaning of these Mantras -
In Manushya rites, Nivita way is prescribed. That's why the wise should perform Manushya rites, as well as rites such as Rishi Tarpana, with sacred thread in the Nivita way. For rites related to the Manes, it should be worn in the PrAchinavita way. For rites related to Gods, including Swadhyaya, it should be worn in the Upavita way (on the left shoulder). In this manner, one becomes endowed with the sign of divinity (devachinhameva kritam bhavati). One should not sit on the seat and chant the Mantras. Therefore, one should stand and chant, so that everyone can hear the chanting. When the aim is attaining the heavens, the chanting should not be done while seating on the seat (AsanAsin)...
This AnuvAka itself has more references to the Heavens mentioned as either Devaloka or Suvarga like- "Devalokam chaiva manushyalokam chAbhi jayati." and "Tira iva vai suvargo lokah suvargamevasmai lokam.."
Suvargam vA ete lokam yanti ye satramupayantyabhindhata eva dikshAbhirAtmAnam shrapayanta ..
The performer of the Samvatsara Satra goes to heaven. Therefore, for earning the qualification one needs to achieve the purification of soul and body by DikshA..
This AnuvAka again has more references to Suvarga like - "nitvA suvargam lokam yanti" and "suvargam lokamayAmeti "
AdityA akAmayanta suvargam lokamiyAmeti te suvargam lokam na prAjAnanna suvargam lokamAyanta etam shattrimsha drAtramapashyantamAhaharantenAyajanta tato vai te suvargam lokam prAjAnanat suvargam ....
In ancient times, the Adityas once desired to go to heaven, but unable to find the correct way, they were not successful in their venture. Then they, after investigating upon the reasons (of failure), devised the validity of the Yajna called "Shattrimshat RAtra Yajna" (done over a span of 36 days) and upon performing themselves that Yajna, discovered the correct path to the heaven and attained it.
KYV 7th KAnda, 4th Prapathaka, AnuvAka 6.
Yet another reference:
PrajApatih suvargam lokamaittam devA yenayena chandhasAhanu prAyunjata tena nAhapnuvanta etA dvAtrimshatam rAtrirapashyaandvAtrimshad aksharAhanushtugAnushtubhah ....
When PrajApati went to heavens, the Gods desired thus- "We will also travel along with him and attain the heavens" and they performed a Yajna with a particular Chandah, but they were not successful in getting their desires fulfilled. Then they initiated a special Yajna called DvAtrimshat Yajna and then they were successful..
Also, in the Vedas, for referring to the heaven, Swarga is not the only word that is used. Other words like Diva and Dyuh are also used more frequently.
Few examples like that are found in the Rig Vedokta Devi Suktam:
aham dyAvAprithivi A vivesha ||
I have permeated heaven and earth.
paro diva para enA prithivyA ||
Far beyond the heavens, far beneath the earth.
Rig Veda 10.125.8