Based on prior knowledge, the Oldpeak feature in coronary angiography represents the measurement of ST depression. ST depression is a measure of the downward displacement of the ST segment of the electrocardiogram (ECG) in relation to the baseline. It indicates the severity of myocardial ischemia, which is a significant indicator of heart disease.

To analyze the relationship between the Oldpeak feature and the presence of heart disease, we can compare the average Oldpeak values for the "no" and "yes" target classes and observe any significant differences.

Here is the dictionary containing the possible Oldpeak values for each target class:

```json
{
    "no": [0.0, 1.5, 2.0, 2.5, 4.0],
    "yes": [1.0, 3.0, 3.5, 5.0, 6.0]
}
```

These values are just examples and may not represent the overall distribution of Oldpeak values accurately. To determine the appropriate ranges of values, it would be essential to analyze a dataset specifically for coronary angiography with corresponding heart disease labels.